ChatGPT answers, unedited

Yes. For a small agency moving email off shared hosting, I’d separate VPS hosting from email hosting rather than run mail yourself.

Good options:

• Zoho Mail — inexpensive, custom domains, migration tools, SPF/DKIM/DMARC, and scales well as users increase. Zoho Zoho
• Fastmail — polished, lightweight email hosting with custom domains, aliases, shared addresses, and straightforward migration. Fastmail
• Microsoft 365 — better if clients need Outlook, Office, Teams, shared mailboxes, etc.
• Google Workspace — similar idea if the agency is already Google-centric.

For an agency specifically, Zoho Mail or Fastmail are worth looking at if you want the VPS to handle websites/apps while a specialist handles email deliverability, spam filtering, backups, and mailbox infrastructure.

If you're talking about hosting email for your agency's clients (multiple domains and potentially dozens/hundreds of mailboxes), that's a different category—I can suggest platforms designed specifically for that model.

Yes. For a small agency moving away from shared hosting email, I would usually avoid running mailboxes directly on the VPS unless you have a strong reason. Email hosting is one of the services where reputation, spam filtering, DKIM/SPF/DMARC management, backups, and deliverability are often more work than the server itself. Dedicated email providers can attach to your domain while your website runs on your VPS. StackBriefly

Good options depending on how your agency operates:

For an agency specifically, the key question is usually how many real users vs. how many addresses you need:

Scenario A: 5–20 employees, each with their own inbox

Use:

• Google Workspace
• Microsoft 365
• Zoho Mail
• Fastmail

Example:

• alice@agency.com
• bob@agency.com
• designer@agency.com

Scenario B: Few people, lots of client-facing addresses

Look for aliases/shared mailboxes:

Example:

• hello@agency.com
• support@agency.com
• billing@agency.com
• clientname@agency.com

A cheaper model may work better because you do not want to pay for 30 mailboxes when only 5 people read them.

Scenario C: You want the VPS to handle everything

You can self-host with tools like:

• Mailcow
• iRedMail
• Modoboa
• Mail-in-a-Box

But for an agency I would only choose this if you are comfortable managing:

• IP reputation
• reverse DNS
• spam filtering
• blacklists
• backups
• DKIM/SPF/DMARC
• security updates

A common architecture is:

Domain DNS
   |
   +-- A record -> VPS (website/app)
   |
   +-- MX records -> Email provider
   |
   +-- SPF/DKIM/DMARC -> Email provider

The VPS handles your sites/apps; the email provider handles mail delivery.

For a small agency migration, my shortlist would usually be:

1. Zoho Mail — if keeping costs low matters.
2. Google Workspace — if clients expect Google collaboration.
3. Microsoft 365 — if clients send lots of Office files.
4. Fastmail — if you want clean email without a big suite.

If you tell me roughly number of staff, number of domains, and whether you need shared inboxes (support@, sales@, etc.), I can narrow it down.

Domain DNS
   |
   +-- A record -> VPS (website/app)
   |
   +-- MX records -> Email provider
   |
   +-- SPF/DKIM/DMARC -> Email provider

The VPS handles your sites/apps; the email provider handles mail delivery.

For a small agency migration, my shortlist would usually be:

1. Zoho Mail — if keeping costs low matters.
2. Google Workspace — if clients expect Google collaboration.
3. Microsoft 365 — if clients send lots of Office files.
4. Fastmail — if you want clean email without a big suite.

If you tell me roughly number of staff, number of domains, and whether you need shared inboxes (support@, sales@, etc.), I can narrow it down.

Yes. For a small agency moving from shared hosting to a VPS, I would usually not host email on the VPS itself unless you specifically want to become your own mail administrator. Running mail servers means handling spam reputation, blacklists, DKIM/SPF/DMARC, backups, filtering, security updates, and deliverability.

The scalable options usually fall into these categories:

1. Managed business email (best default)

These give you proper domain mailboxes like you@agency.com, client@agency.com, shared mailboxes, aliases, admin controls, and migration tools.

• workspace.google.com — Good if your agency already uses Gmail, Drive, Docs, and Calendar. Scales cleanly from a few users upward. StackBriefly
• microsoft.com — Better fit if clients expect Outlook/Exchange compatibility or you use Office/Teams. StackBriefly
• zoho.com — Often attractive for small agencies because it focuses on domain email and admin features without requiring a full Google/Microsoft ecosystem. StackBriefly
• fastmail.com — A lighter email-focused option with custom domains and less suite overhead. StackBriefly

2. Email hosting built for many domains/mailboxes

If your agency manages multiple client domains and wants many mailboxes without paying per-user suite pricing, look at providers designed around domain hosting:

• mxroute.com — Popular among agencies/hosting resellers because the model is closer to traditional hosted email: multiple domains, mailboxes, aliases, and reseller-style management. digitalhosting.com
• migadu.com — Designed around multiple domains and aliases; can be cost-effective for small organizations with many addresses. digitalhosting.com

3. Self-hosted on your VPS (possible, but usually not ideal)

Common stacks:

• mailcow.email
• mailinabox.email
• iredmail.org

Advantages:

• Full control
• Unlimited mailboxes (hardware permitting)
• Can bundle with your VPS offering

Disadvantages:

• Your VPS IP reputation matters
• Deliverability can become a daily job
• Backups and spam filtering are your responsibility

What I would choose for an agency

A typical setup:

A common migration pattern is:

1. Move websites/apps to the VPS.
2. Leave DNS management where it is.
3. Point MX records to the email provider.
4. Configure SPF, DKIM, and DMARC.
5. Migrate old mailboxes via IMAP.

For an agency, I would generally keep web hosting and email hosting separate. A VPS outage or IP reputation issue should not take down client email.

If you mean your agency's own email versus offering email hosting to your clients, the best choice changes quite a bit.

Yes. In fact, for a small agency moving web hosting from shared hosting to a VPS, I’d generally recommend not hosting email on the VPS itself. Keep the VPS for websites/apps and use a dedicated email-hosting provider.

Good options

• zoho.com — probably my first choice for a small agency. It supports custom domains, multiple mailboxes, aliases/groups, SPF/DKIM/DMARC, admin controls, and migration from IMAP providers. It can scale from a handful of users to much larger organizations. Zoho Zoho
• microsoft.com — better if the agency already lives in Outlook/Word/Excel/Teams and wants a full business suite.
• workspace.google.com — excellent if the agency prefers Gmail/Drive/Docs and wants very polished collaboration.
• fastmail.com — worth considering if you mainly need excellent hosted email without a huge collaboration suite.
• migadu.com — particularly interesting for agencies managing multiple domains and lots of addresses/aliases, where traditional per-user pricing can become annoying.

For an agency specifically

There's an important distinction between:

10 employees = 10 mailboxes

and

10 employees + 20 client domains + dozens of aliases/forwarders.

If you're an agency hosting email for your own agency, Zoho/Microsoft 365/Google Workspace are straightforward.

If you're planning to provide email hosting to your clients—e.g.:

• alice@client1.com
• bob@client1.com
• info@client1.com
• john@client2.com
• support@client3.com

—then I'd look much more closely at Migadu or an email-hosting platform designed around multiple domains, because the economics and administration can be very different.

Also, you don't need to move the domains themselves. Your registrar/DNS can remain wherever it is; you'd simply point each domain's MX records to the email provider. Zoho explicitly supports adding existing domains and changing their MX records, for example. Zoho

If you tell me roughly how many domains, mailboxes per domain, and total users you expect (e.g. 15 domains / 3–5 mailboxes each / ~50 users), I can compare Zoho vs Migadu vs Microsoft 365 vs self-hosting on the VPS and tell you which is likely cheapest and easiest to administer.

Yes. For a small agency moving away from shared web hosting + cPanel-style mailboxes, you usually want dedicated email hosting, not email running on the same VPS as your websites. Running your own mail server on a VPS is possible, but deliverability, spam reputation, backups, DKIM/SPF/DMARC, and IP reputation become ongoing jobs.

Good options depend on whether you manage your own agency mail or client domains/mailboxes.

Best fits for an agency with multiple domains

1. Agency-focused / multi-domain mailbox hosting

shipmail.to

• Designed around agencies with multiple client domains.
• Supports domain-based mailboxes and shared inbox workflows.
• Useful if you need addresses like: - info@clientdomain.com
• support@clientdomain.com
• accounts@youragency.com
• Better fit than normal employee email suites when you manage many client inboxes. Shipmail

2. zoho.com

Good for:

• Small agencies
• Multiple domains
• Lower cost than Google Workspace/Microsoft 365
• Admin controls, aliases, groups, mobile apps

Typical setup:

• Agency domain → your team mailboxes
• Client domains → separate organizations or domains (depending on how you want to administer them)

3. fastmail.com

Good for:

• Email-only hosting
• Custom domains
• Privacy-focused teams
• Lightweight administration

Less ideal if you need heavy collaboration features.

4. microsoft.com or workspace.google.com

Best if your agency wants:

• Calendar
• Shared documents
• Team collaboration
• Enterprise-grade admin/security

They are usually priced per user, so costs can rise if you create many client mailboxes. LetterDuck Fit Small Business

If you specifically want "like cPanel email, but better"

Look at dedicated email hosts:

• dreamhost.com — standalone domain email that works even if your website is hosted elsewhere. DreamHost
• purelymail.com — very low-cost email hosting for domains (good for many small mailboxes, less polished).
• mxroute.com — popular among hosting providers/resellers because it supports many domains and mailboxes.

If your agency wants to resell email to clients

Look for:

• multi-domain support
• reseller/white-label options
• mailbox quotas
• API provisioning
• migration tools
• DKIM/SPF/DMARC automation

A VPS-style email platform may fit here. For example, some providers offer VPS email tiers aimed at MSPs/agencies with multiple domains and white-label requirements. Infinity Data Center

I would avoid

• Hosting mailboxes directly on the same VPS as WordPress/client sites unless you have strong mail administration experience.
• "Unlimited email" from cheap shared hosting providers if email reliability matters.
• A single Gmail/Outlook account with lots of forwarding rules for client domains.

For a typical small web/design/dev agency, a practical architecture is:

Websites: VPS/cloud hosting
DNS: Cloudflare or registrar DNS
Email: dedicated email provider
Authentication: SPF + DKIM + DMARC
Backups: separate mailbox backup/export system

If you tell me roughly:

1. number of domains you manage (5? 50? 500?),
2. number of mailboxes per domain, and
3. whether clients should log in themselves or your agency manages all inboxes,

I can narrow this to the best 2–3 choices.

Yes. In fact, for a small agency hosting multiple client domains, I’d strongly consider keeping email separate from the VPS rather than running your own mail server.

Best fit: Migadu

migadu.com is particularly well suited to an agency model.

• Multiple domains under one account
• Unlimited mailboxes/addresses on its paid plans, rather than charging per mailbox
• Designed specifically for agencies that host clients' domains
• Admin controls let you organize clients/domains and restrict users to particular domains
• Supports standard SMTP, IMAP, POP3 and webmail
• You can start small and increase capacity as your agency grows. Migadu Migadu Migadu
• Current plans are $9/mo, $29/mo, and $99/mo, with the higher tiers increasing sending limits and storage rather than simply charging you for every mailbox. Migadu

That pricing model is especially attractive if, for example, you have 15 client domains with 5–20 addresses each.

Other good options

Fastmail is another strong choice if the priority is a polished business email experience rather than lots of client mailboxes. Its business plans support custom domains, shared addresses, admin controls, and migration from an existing provider. Fastmail Fastmail

fastmail.com

Zoho Mail is worth considering if you want more of a conventional business-suite/admin experience. It supports custom-domain hosting, centralized administration, and IMAP migration from existing hosts. Zoho Zoho

zoho.com

What I'd do in your situation

I'd structure it like:

VPS
→ websites, databases, applications, DNS management, backups

Migadu
→ client1.com email
→ client2.com email
→ client3.com email
→ etc.

Then point each domain's MX records to the email provider. Your VPS doesn't need to accept or deliver ordinary mailbox email.

That's preferable to running Postfix/Dovecot yourself because email deliverability, spam reputation, IP reputation, DKIM/DMARC, blacklists, mailbox storage, backups, and abuse handling become someone else's problem.

If you tell me roughly how many domains, mailboxes per domain, and total users you're expecting (e.g. “20 domains, ~8 mailboxes each”), I can compare Migadu vs Zoho vs Fastmail vs self-hosting on the VPS and give you the most economical architecture.

Yes. In fact, for a small agency moving websites from shared hosting to a VPS, I’d generally recommend not putting the agency’s email on the VPS. Keep the VPS focused on web/app hosting and use a dedicated hosted-email provider for the domain mailboxes. This avoids taking on mail-server reputation, spam filtering, backups, SPF/DKIM/DMARC, and deliverability yourself. VPSDime SSD Nodes

Good options

• zoho.com — probably the best value if you mainly need person@agency.com mailboxes. It supports custom domains, admin controls, SPF/DKIM/DMARC, and migration from IMAP providers. Zoho
• fastmail.com — excellent if you want email-first hosting rather than an entire office suite. Its business plans support custom domains, shared addresses such as support@, and mixing different plans/users as your agency grows. Fastmail
• workspace.google.com — best if the agency already lives in Gmail/Google Drive/Docs/Meet. It's more expensive than mailbox-only services, but gives you the complete collaboration stack. Fit Small Business
• microsoft.com — similar idea if your clients/team are heavily invested in Outlook, Office, Teams, and OneDrive. TechRepublic

What I'd choose for an agency

If you're talking about something like 5–30 people, multiple client domains, and primarily needing reliable domain mailboxes, I'd shortlist Zoho Mail vs Fastmail.

One particularly useful feature for an agency is multiple domains. You can have things like alice@agency.com, bob@agency.com, and potentially mailboxes/addresses for client-owned domains without tying email hosting to the web server.

One important distinction

If by "scalable email hosting" you mean normal business correspondence, these providers are what you want.

If you mean sending large volumes of marketing/cold/outreach email, that's a different infrastructure problem. You shouldn't use your ordinary employee mailboxes for that; you'd typically separate transactional/outbound sending from the agency's primary mail system.

For the VPS migration itself, I'd structure it:

Shared hosting → VPS for websites/apps
Hosted email provider → all domain mailboxes
DNS provider → manages DNS/MX/SPF/DKIM/DMARC
Transactional email provider → website/app-generated mail

That separation makes future migrations dramatically easier and prevents a web-server move from becoming an email outage. Hostperl

If you tell me roughly how many mailboxes, how many domains, and whether you need just email or also calendars/Drive/Office, I can narrow this down to the cheapest sensible setup and estimate the monthly cost.

Yes. In fact, for a small agency moving from shared hosting to a VPS, I’d generally keep email separate from the VPS rather than running mailboxes on the VPS itself. You get better deliverability, backups, spam filtering, and less operational overhead.

Good options:

• Zoho Mail — probably the first one I’d investigate for an agency that mainly needs name@domain.com mailboxes. It supports custom domains, administration, and is positioned as a scalable business-email service. Zoho
• Fastmail — excellent if you want email hosting rather than a whole office suite. It supports custom domains, aliases, calendars, and multiple users. Recent comparisons put its business plan around $5/user/month. StackBriefly TechRepublic
• Google Workspace — best if the agency already wants Gmail + Drive + Docs + Calendar + Meet. It's more expensive if you only need mailboxes, but very easy to scale as employees are added. Fit Small Business
• Microsoft 365 — similar story if the agency prefers Outlook/Exchange/Office/Teams. StackBriefly
• Migadu — particularly interesting if you're an agency managing multiple client domains. Its pricing model is more oriented toward accounts/domains and can make sense for a technical operator managing lots of addresses. Sekin

The important distinction for an agency

If you mean something like:

VPS hosts websites, while one email service hosts alice@agency.com, bob@agency.com, support@agency.com, plus mailboxes for several client domains

then I'd specifically look at Migadu, Zoho, or a similar multi-domain provider, rather than automatically buying Google Workspace seats for every address.

Also distinguish between:

• Real mailbox: alice@client.com with its own login/inbox
• Alias: info@client.com forwarding into someone's mailbox
• Shared/group address: support@client.com used by multiple people

That distinction can make a huge difference in cost for an agency.

What I'd recommend

For a small agency, I'd probably structure it:

Registrar/DNS → VPS for websites → dedicated hosted-email provider for mail

and configure SPF + DKIM + DMARC properly on every domain.

I would not put the agency's production email server on the new VPS unless you specifically want to become responsible for mail reputation, IP reputation, spam filtering, backups, queue management, blacklists, etc.

If you tell me roughly how many domains, mailboxes, and aliases you need (e.g. 5 domains / 20 mailboxes / 50 aliases), I can compare the most economical setup and show you what I'd use.

Yes. For a small agency moving from shared hosting to a VPS, I would generally avoid running email directly on the VPS unless you specifically want to become your own mail administrator. Email delivery, spam reputation, blacklists, DKIM/DMARC, backups, and mailbox reliability are usually more work than hosting websites. Dedicated email hosting is usually the cleaner architecture. Fit Small Business

Good options depending on your agency model:

For an agency specifically, I would think about the mailbox structure:

Option A — You manage client websites only

Use one email provider for your agency:

• you@agency.com
• support@agency.com
• billing@agency.com
• sales@agency.com

A service like Zoho Mail or Fastmail is usually enough. Fit Small Business AI Emaily

Option B — You resell hosting and email to clients

Look for:

• multiple custom domains
• unlimited aliases
• mailbox provisioning
• admin delegation
• migration tools
• API support
• predictable pricing

Migadu is one example aimed at multi-domain setups. AI Emaily

Option C — You want full control on your VPS

You can self-host with tools like:

• Mailcow
• Mail-in-a-Box
• iRedMail
• Modoboa

But expect to manage:

• Postfix/SMTP reputation
• spam filtering
• DNS records (SPF/DKIM/DMARC)
• backups
• IP reputation
• monitoring

A VPS IP with poor reputation can cause client emails to land in spam, which is why many agencies separate web hosting and email hosting.

A common professional setup is:

• VPS: websites/apps/databases
• Email host: mailboxes
• DNS provider: manages MX/SPF/DKIM/DMARC
• Transactional email service: app/site notifications

For a small agency moving off shared hosting, my shortlist would probably be:

1. Migadu if you will host many client domains.
2. Zoho Mail if you want mainstream business email at a reasonable cost.
3. Google Workspace/Microsoft 365 if your team depends on collaboration tools. Fit Small Business TechRepublic

If you tell me roughly how many domains and mailboxes you expect (e.g., 20 clients × 5 mailboxes each), I can suggest the most cost-effective architecture.

Yes. For a small agency moving from shared hosting to a VPS, I would generally avoid hosting email directly on the VPS unless you specifically want to become an email administrator. Mail delivery, spam reputation, backups, DKIM/SPF/DMARC, blacklists, and mailbox reliability are usually more work than the VPS itself.

You have a few good models:

1. Managed business email hosting (best default)

These give you domain-based mailboxes like name@agency.com, support@agency.com, etc.

These are usually the easiest migration path from cPanel/shared-host email. Fit Small Business TechRepublic

2. Agency-focused / multi-domain email platforms

If your agency manages multiple client domains and needs mailboxes like:

• hello@client1.com
• support@client2.com
• billing@client3.com

then look at platforms designed around agencies:

• atriomail.com — white-label email hosting aimed at agencies/resellers, with provisioning, DNS automation, and integrations. Atriomail
• shipmail.to — focused on agency/shared inbox workflows and multiple domains. Shipmail Shipmail

These are more attractive if email is something you provide as part of your agency service.

3. Self-hosted email on your VPS (possible, but higher maintenance)

Common stacks:

• mailcow.email
• mailinabox.email
• iredmail.org

Pros:

• Full control
• Unlimited domains/mailboxes (hardware permitting)
• Can integrate with your hosting platform

Cons:

• You own: - spam filtering
• IP reputation
• backups
• monitoring
• security updates
• outbound deliverability

For a small agency, I would usually only do this if email hosting itself is part of your business offering.

A practical agency setup

A common architecture is:

VPS
├── Websites
├── Databases
├── Apps
└── No email

Email provider
├── MX records
├── SPF
├── DKIM
├── DMARC
└── Mailboxes

Then your DNS simply points:

• A records → VPS
• MX records → email provider

My recommendation by scenario

• 5–50 internal staff mailboxes: Google Workspace or Microsoft 365
• Budget-conscious agency: Zoho Mail
• Agency managing many client domains: Atriomail or Shipmail-style platform
• You want to resell email hosting: white-label provider
• You want maximum control: Mailcow on a dedicated VPS

If you tell me roughly:

1. number of mailboxes now and expected in 2–3 years,
2. whether these are your agency accounts or client accounts, and
3. whether you need shared inboxes (support@, sales@, etc.),

I can narrow it down to the best architecture.

Yes. If by “scalable” you mean multiple client domains, lots of domain-based mailboxes, and not paying separately for every mailbox, there are a few good options.

My first pick: Migadu

Migadu is unusually well-suited to an agency model. Its pricing is per account rather than per mailbox, and you can host unlimited domains and unlimited mailboxes subject to sending/usage quotas. Migadu explicitly says agencies use it to host clients' email domains under one account. Migadu

Current plans include:

• Mini — $9/month or $90/year - Unlimited domains
• Unlimited mailboxes/addresses
• 1,000 incoming / 100 outgoing messages per day
• 30 GB soft storage
• Standard — $29/month - 3,000 incoming / 500 outgoing per day
• 100 GB+ soft storage
• Maxi — $99/month - 10,000 incoming / 2,000 outgoing per day
• 500 GB+ soft storage

The important distinction is that those limits are per account, not per mailbox. Migadu

So, for example, an agency managing:

clientA.com → 8 mailboxes
clientB.com → 15 mailboxes
clientC.com → 4 mailboxes

could have all of those under one Migadu account rather than buying 27 individual mailbox subscriptions.

If you want to use your VPS: Mailcow

If the goal is specifically “we're moving to a VPS and want email infrastructure on that VPS”, I'd look at Mailcow.

It's a full self-hosted mail platform rather than merely an SMTP server: domains, mailboxes, aliases, webmail, spam filtering, DKIM, etc. You retain control over the VPS and can add domains/mailboxes without a SaaS provider charging per mailbox.

The catch is deliverability and maintenance. Running mail yourself means you're responsible for IP reputation, reverse DNS, SPF/DKIM/DMARC, backups, monitoring, blocklists, security updates, and making sure your VPS provider permits outbound SMTP.

There are also managed Mailcow offerings. For example, DigitalFyre currently advertises a managed private Mailcow server starting at $85/month with unlimited mailboxes, domains and aliases, which is an interesting middle ground between SaaS email and operating it yourself. DigitalFyre Knowledge Base

Other good SaaS choices

Fastmail is excellent if you're primarily hosting your own agency's email rather than dozens of client domains. Its business plans are per-user, but it supports custom domains, shared addresses, admin controls and third-party mail clients. Fastmail

Zoho Mail is another strong conventional business-email option, particularly if you want a more traditional admin/productivity suite. Its Enterprise tier supports custom configurations and pooled storage. Zoho

What I'd choose for an agency

One important point: don't necessarily put your website VPS and mail server together. Email is one of the services where outsourcing the operational/deliverability burden can be worth far more than the VPS savings.

If you tell me roughly how many domains, mailboxes, and emails/day the agency expects (e.g. “20 domains / 100 mailboxes / normal business email”), I can compare the economics of Migadu vs Mailcow-on-VPS vs Zoho vs Google Workspace for that exact setup.

Yes. For a small agency moving websites from shared hosting to a VPS, I’d keep email separate from the VPS rather than running your own mail server. It’s much easier to scale, and you avoid having to manage spam reputation, DKIM/DMARC, blacklists, backups, and mail-server security.

A few good fits:

• migadu.com — probably the most interesting for an agency. It prices by account/usage rather than per mailbox, supports unlimited addresses and domains, and explicitly supports agencies hosting client domains under one account. Its Standard plan is currently $29/month and Maxi $99/month. Migadu Migadu
• zoho.com — best conventional business option. You can host multiple custom domains, create individual mailboxes and aliases, and migrate existing mailboxes from IMAP/other providers. Paid plans are per user, so costs rise with the number of actual users. Zoho Zoho
• fastmail.com — excellent if it's primarily your agency's own staff. Its business plans support custom domains, shared addresses such as support@domain.com, admin controls, and mixing different plans among users. Fastmail
• purelymail.com — extremely inexpensive. It currently advertises $10/year with no hard limits on users, domains, or storage, although heavy usage can move you to resource-based pricing. I'd consider it more for cost-sensitive setups than client-facing agency infrastructure. Purelymail

For an agency specifically

If you're talking about something like:

VPS hosts 20–50 client websites → each client has their own domain → each domain may have 5–20 mailboxes

then Migadu is particularly worth investigating because its model maps much better to that structure than paying separately for every mailbox. Migadu specifically says agencies use it to host client domains under one account. Migadu

Your architecture could simply be:

Registrar/DNS → VPS for websites
Registrar/DNS → email provider for MX
Cloud backups → separate backup provider

The VPS doesn't need to handle mail at all.

If you tell me roughly how many domains and mailboxes you need now (and expected in 1–3 years), I can compare Migadu vs Zoho vs Fastmail and work out the approximate monthly cost and the cleanest agency setup.

Yes. In fact, I’d generally keep email off the VPS. Let the VPS handle websites/apps and use a dedicated hosted-email provider for the domain mailboxes. That avoids you having to manage spam reputation, IP blacklists, DKIM/DMARC, backups, mailbox storage, and deliverability.

For a small agency, I'd shortlist:

• zoho.com — probably the best value if you primarily need person@agency.com mailboxes. It supports custom domains, SPF/DKIM/DMARC, admin controls, and migration from IMAP/other providers. Zoho
• fastmail.com — excellent if you want email-focused hosting without paying for a whole office suite. Particularly attractive for a technically managed agency.
• workspace.google.com — best if the agency also wants Gmail, Drive, Docs, Meet, shared calendars, etc.
• microsoft.com — similar idea if the team lives in Outlook/Office/Teams.
• proton.me — worth considering when privacy is a major requirement; custom domains and the necessary MX/SPF/DKIM/DMARC setup are supported. Proton

But there's another interesting option

If by "scalable" you mean you manage lots of client domains and want to provision mailboxes cheaply, rather than simply 10–30 employees on one domain, I'd look at a multi-domain email hosting platform rather than Workspace.

That's a different requirement. For example, you might have:

client-a.com
  alice@client-a.com
  info@client-a.com

client-b.com
  bob@client-b.com
  sales@client-b.com

youragency.com
  you@youragency.com
  support@youragency.com

In that scenario, domain-level pricing, aliases, catch-alls, mailbox provisioning, API/admin automation, and multi-domain management become much more important than whether the service includes Google Docs.

If that's what you're building, tell me roughly how many domains and mailboxes you expect (e.g. 20 domains / 100 mailboxes) and whether you want managed hosting or are willing to run the mail server yourself. I can narrow it down to the 3–4 platforms that actually fit that model.

Yes. If you're moving the website/app hosting to a VPS but want email to remain professionally hosted, I’d actually recommend not running mailboxes on the VPS. Email has very different reliability, spam-reputation, backup, and deliverability requirements.

For a small agency with multiple domains and potentially growing mailbox counts, these are the options I'd look at:

• Zoho Mail — probably the best budget/scalability option. Custom domains, individual mailboxes, aliases, admin controls, and migration tooling. Current comparisons put Mail Lite around $1/user/month on annual billing. StackBriefly LetterDuck
• Fastmail — excellent if you primarily want email hosting without paying for a full office suite. Strong custom-domain, alias, IMAP/SMTP and calendar support. StackBriefly ChoicePilot
• Google Workspace — more expensive, but a very good agency choice if clients/staff already use Gmail, Drive, Docs and Calendar. Fit Small Business
• Microsoft 365 — particularly good if the agency is Outlook/Office-oriented. Exchange gives you proper business mailboxes, aliases and shared mailboxes. ChoicePilot
• Proton Mail — worth considering if privacy is a major selling point, though it's less compelling purely as a cost-effective agency mail platform. StackBriefly

But there's another option

If by "scalable" you mean something like:

"We have 15 domains, 80 mailboxes today, and might have 300 later. We want one admin system and don't want to pay a full productivity-suite license for every mailbox."

Then I'd also investigate multi-domain email hosting specifically, rather than Google/Microsoft.

There are services designed around the model:

agency → domains → mailboxes → aliases → forwards → shared addresses

That can be considerably cheaper than paying $5–$15+ per user for every address.

And if you're technically comfortable administering Linux, mailcow or a similar mail stack on a separate VPS is another possibility—but I'd be cautious about this for client-facing agency email. Self-hosted mail means you're responsible for IP reputation, DKIM/SPF/DMARC, spam filtering, backups, blacklists, monitoring, TLS, abuse handling, and keeping delivery reliable.

What I'd probably do

For a small web/design/marketing agency, I'd separate the infrastructure:

VPS

• Websites
• Apps
• Databases
• Client projects
• DNS management

Managed email provider

• person@agency.com
• client@clientdomain.com
• sales@...
• support@...
• aliases/forwarders
• spam filtering
• DKIM/SPF/DMARC
• mailbox backups/retention

That way moving from shared hosting doesn't turn your VPS into a critical email server.

If you tell me roughly how many domains and mailboxes you have now (and expected in 1–3 years), I can narrow this down to the 2–3 providers that make the most financial and operational sense, including the per-mailbox vs per-domain pricing model.

What I'd probably do

For a small web/design/marketing agency, I'd separate the infrastructure:

VPS

• Websites
• Apps
• Databases
• Client projects
• DNS management

Managed email provider

• person@agency.com
• client@clientdomain.com
• sales@...
• support@...
• aliases/forwarders
• spam filtering
• DKIM/SPF/DMARC
• mailbox backups/retention

That way moving from shared hosting doesn't turn your VPS into a critical email server.

If you tell me roughly how many domains and mailboxes you have now (and expected in 1–3 years), I can narrow this down to the 2–3 providers that make the most financial and operational sense, including the per-mailbox vs per-domain pricing model.

Yes. For a small agency hosting multiple domain-based mailboxes, there are a few good approaches—and one stands out if you want to move away from shared hosting without making email another VPS-maintenance headache.

Best fit: Migadu

migadu.com is particularly well suited to agencies.

• Multiple client domains under one account.
• Unlimited addresses/mailboxes within the plan's usage quotas.
• Flat account pricing rather than charging separately for every mailbox.
• Multiple administrators and the ability to restrict admins to particular domains.
• SMTP, IMAP, POP3 and webmail, so you're not locked into a proprietary mail client.
• Mailbox quotas and domain-health monitoring.
• Backups and standard DNS controls.
• Their current agency-oriented plans range from $9/month to $99/month, depending on capacity. Migadu Migadu

That's a pretty attractive model if, for example, you have 15 client domains with 3–20 mailboxes each. You can put the mail on Migadu while putting websites/apps/databases on your VPS.

migadu.com

If you specifically want email on your VPS: Mailcow

docs.mailcow.email is probably the option I'd investigate.

It gives you a complete self-hosted mail platform—Postfix/Dovecot, webmail, spam/virus filtering, calendars, contacts, domain administration, etc.—rather than trying to assemble Postfix + Dovecot + Rspamd yourself.

The catch is that you become the mail provider. Mailcow's documentation recommends at least 6 GB RAM + 1 GB swap, with 8 GB being a reasonable starting point for roughly 5–10 users. Mailcow Documentation

For an agency, that means dealing with:

• IP reputation and blacklists
• SPF/DKIM/DMARC
• reverse DNS/PTR
• backups
• spam filtering
• security updates
• monitoring
• outbound deliverability
• VPS provider port-25 restrictions

So I'd generally keep websites on the VPS but outsource mail unless you specifically want to operate your own mail infrastructure.

Zoho Mail is another strong choice

zoho.com is more conventional business email. It supports custom domains, migration from existing IMAP providers, multiple data-center locations, retention/recovery, and business administration. Zoho

The important distinction is pricing: Zoho is much more mailbox/user oriented, whereas Migadu is unusually attractive when an agency has lots of domains and addresses.

What I'd choose

For your particular migration, I'd lean toward Migadu. It lets you separate the two concerns cleanly: the VPS becomes your web/application infrastructure, while a specialized provider handles the notoriously annoying parts of running email. Migadu explicitly targets agencies managing client domains, which is a very close match to your use case. Migadu Migadu

If you tell me roughly how many domains, mailboxes, and total mailbox storage you're dealing with, I can compare Migadu vs Zoho vs Mailcow with the likely monthly cost and migration architecture.

Yes. If the goal is “move websites to a VPS, but keep email off the VPS”, that’s actually a setup I’d recommend for a small agency. Self-hosting mail alongside your VPS tends to create unnecessary deliverability, spam, backup, and reputation-management work.

Best fits for an agency

• migadu.com — probably my first choice for your use case.

It is specifically designed around multiple domains and many mailboxes/addresses, rather than charging you for every mailbox. Their agency tooling supports hosting client domains under one account, multiple administrators, per-domain access restrictions, and mailbox limits. Migadu Migadu
Current plans include Standard at $29/month and Maxi at $99/month, with unlimited addresses/domains and substantially higher sending/storage allowances as you scale. Migadu

• mxroute.com — excellent if you want cheap, straightforward mail hosting.

It offers unlimited domains and accounts on its plans, with SMTP/IMAP/POP3, aliases and forwarding. Current pricing starts around $59/year, with larger storage tiers available. It also has reseller plans with a white-label control panel, which is interesting if you want to offer email as part of your agency service. MXroute

• fastmail.com — better for your own agency team than for lots of client domains.

It has excellent business administration, custom domains, shared addresses, calendars, and migration tooling, but its model is more per-user/per-seat oriented. Fastmail

• zoho.com — good if you want a conventional business suite.

It supports custom domains and has IMAP/POP migration tooling, making it a reasonable choice when migrating existing shared-hosting mailboxes. Zoho Zoho

What I'd do in your situation

I'd structure it like:

                    ┌── VPS
                    │   Websites
                    │   Apps
                    │   Databases
                    │
Domain ─────────────┤
                    │
                    └── Email provider
                         ├── client1.com
                         │    ├── john@
                         │    ├── sales@
                         │    └── info@
                         ├── client2.com
                         │    ├── jane@
                         │    └── support@
                         └── agency.com
                              ├── you@
                              └── admin@

The VPS handles web hosting, while the email provider handles MX, SMTP, IMAP, spam filtering, DKIM, etc.

For an agency specifically, Migadu is unusually well matched because you can put multiple client domains under the same administrative umbrella without turning every mailbox into another paid seat. Migadu

MXroute would be my second choice if your priority is keeping costs extremely low and you don't need as sophisticated a multi-client administration layer.

If you tell me roughly how many client domains + mailboxes you expect (e.g. 20 domains / 100 mailboxes), I can compare Migadu vs MXroute vs Zoho and work out the approximate monthly cost and the best migration architecture.

Yes. For a small agency managing multiple client domains, there are a few good options, but one stands out for your particular setup:

Best fit: Migadu

migadu.com is specifically designed around multiple domains and lots of mailboxes/aliases without charging per mailbox.

• One account can host multiple client domains.
• Mailboxes and addresses are not individually billed; pricing is based on account-wide usage limits. Migadu Migadu
• It supports standard SMTP, IMAP, POP3 and webmail, so clients aren't locked into a proprietary mail client. Migadu
• It has agency-oriented administration, including multiple admins and the ability to restrict admins to particular domains. Migadu
• You can set limits on individual domains/mailboxes, which is useful when you're hosting email for clients. Migadu
• Its current published plans range from $9/month for Mini, $29/month Standard, to $99/month Maxi, with the paid plans allowing unlimited addresses/domains subject to the plan's overall quotas. Migadu

That's quite different from Google Workspace/Microsoft 365, where you generally pay per user/mailbox.

Other possibilities

Zoho Mail is worth considering if each client is more of a conventional business needing a polished business-mail suite. It supports custom-domain mailboxes, groups, aliases and IMAP/POP on paid tiers. Zoho Zoho Corporation Zoho

zoho.com

Fastmail is another excellent hosted-email provider, particularly if you value a polished user experience and don't need to manage a large number of client domains. It supports custom business addresses and administrative controls. Fastmail

fastmail.com

For your VPS migration

I would not necessarily put the mail server on the new VPS. Running your own Postfix/Dovecot stack sounds attractive, but deliverability, IP reputation, spam filtering, DKIM/DMARC, reverse DNS, blacklists, backups, and abuse handling become your responsibility.

A setup like this is considerably easier:

Client domains
     │
     ├── client1.com ──┐
     ├── client2.com ──┤
     ├── client3.com ──┼──> Migadu
     └── client4.com ──┘
                         │
                    SMTP / IMAP
                         │
                  Client mail apps

Your VPS handles websites/apps, while a dedicated mail provider handles email infrastructure.

For an agency specifically, Migadu is probably the first one I'd evaluate because its pricing model makes a huge difference if you're going from, say, 10 domains / 40 mailboxes to 50 domains / 200 mailboxes. You're not multiplying your email bill by the number of inboxes. Migadu Migadu

If you tell me roughly how many domains, mailboxes, and emails/day you're expecting, I can compare Migadu vs Zoho vs Google Workspace vs self-hosting and give you the most economical architecture.

Yes. For a small agency moving from shared hosting to a VPS, I’d keep email separate from the VPS rather than running mailboxes on the VPS itself. You can point each domain’s MX records to a dedicated email host while the VPS handles websites/apps.

A particularly good fit is Zoho Mail. zoho.com supports:

• Multiple custom domains and domain-based mailboxes.
• Adding/removing users as the agency grows.
• Aliases/groups such as info@, support@, or billing@ without necessarily requiring a separate person.
• IMAP/POP on paid plans, so clients can use Outlook, Apple Mail, Thunderbird, etc. Zoho Zoho
• Migration from existing mail providers, which makes moving off shared hosting considerably easier. Zoho
• Mail Lite currently starts at $1/user/month annually for 5 GB, with a 10 GB tier, while Mail Premium is $4/user/month annually for 50 GB + 50 GB archival storage. Zoho
• A free tier exists for up to five users/one domain in some data centers, although it lacks IMAP/POP and isn't available everywhere. Zoho

How I'd structure the agency

VPS

• example.com website
• client websites/apps
• databases
• DNS management if desired

Email provider

• you@example.com
• client@example.com
• info@example.com
• support@example.com
• potentially dozens of domains/mailboxes as you take on clients

You simply configure the domains' MX, SPF, DKIM, and DMARC records for the mail provider. The email service remains independent if you later move VPS providers. Zoho explicitly supports the domain-verification → MX → SPF/DKIM setup and mailbox migration workflow. Zoho

If by "agency" you mean you want to host email for your own agency and multiple client domains, there are some more interesting options than Zoho—particularly providers designed around lots of domains/mailboxes at a low cost. I can compare Zoho vs MXroute vs Migadu vs Fastmail vs self-hosting on the VPS, including approximate cost at 25, 100, and 500 mailboxes.

Yes. If by “scalable” you mean multiple client domains + lots of domain-based mailboxes without running the mail server yourself, there are a few good options.

Best fit for an agency: migadu.com

Migadu is unusually well suited to the agency/reseller-style setup you're describing:

• Multiple client domains under one account.
• Unlimited addresses/mailboxes on the paid plans, with usage limits rather than per-mailbox billing.
• Multiple administrators, with the ability to restrict admins to particular domains.
• Mailbox/domain quota controls.
• Standard SMTP/IMAP/POP3, so clients aren't locked into a proprietary mail client.
• Continuous mailbox backups.
• Their current agency offering explicitly describes hosting clients' domains "under a single roof." Migadu Migadu Migadu

The current paid tiers are $9/mo, $29/mo, and $99/mo, with progressively higher sending/storage allowances; importantly, those prices are per account, not per mailbox. Migadu

For an agency moving websites from shared hosting onto a VPS, I'd seriously consider:

VPS → websites/apps
Migadu → all client email

That keeps email isolated from your VPS. I would not put production client mailboxes directly on the VPS unless you specifically want to become an email-infrastructure operator.

Other possibilities

Fastmail is a polished alternative if you have fewer domains and want a more conventional business-mail experience. Its Standard business plan supports custom domains, shared addresses such as support@, shared calendars/contacts, and third-party clients. Fastmail

Zoho Mail is another strong choice, particularly if clients need a broader business suite. It supports custom domain mailboxes, groups and aliases, and has migration tooling. Zoho Zoho Corporation

I would rank them for your particular use case:

*Subject to the account's usage limits.

One thing to distinguish: ordinary hosted email versus cold-email infrastructure. If you're talking about normal person@clientdomain.com, info@, sales@, etc., Migadu is very interesting. If you mean hundreds/thousands of outbound marketing emails per day, that's a different category and I'd use a dedicated transactional/bulk-email provider rather than your mailbox host.

If you tell me roughly how many client domains and mailboxes you expect (e.g. 20 domains / 100 mailboxes), I can compare the economics of Migadu vs Zoho vs Microsoft 365 and suggest the cleanest architecture for the VPS migration.

Yes. For a small agency moving the websites from shared hosting to a VPS, I’d generally recommend not moving the mail server onto the VPS. Keep the VPS for web/apps and use a dedicated managed email host. That avoids a lot of deliverability, spam, IP-reputation, backup, and maintenance headaches. VPS.DO Affordable VPS Server

Best fits for an agency

• migadu.com — probably the most interesting option for an agency

• Designed specifically for multiple domains.
• Pricing is per account rather than per mailbox.
• Their plans allow unlimited addresses and domains within usage quotas.
• They explicitly mention agencies hosting their clients' email domains under one account.
• Current plans range from $9/month to $99/month, with the Standard plan at $29/month and Maxi at $99/month. Migadu
• This is particularly attractive if you have, say, 10 client domains with 3–10 addresses each.
• fastmail.com — excellent for your own agency

• Polished business email, custom domains, admin controls, shared addresses, calendars, etc.
• More conventional per-user pricing.
• Strong choice if you're primarily hosting mail for your own staff rather than acting as an email host for many clients. Fastmail
• zoho.com — good low-cost conventional business option

• Supports custom domains and business administration.
• Has Mail-only plans as well as broader Workplace plans.
• Particularly worth considering if you're price-sensitive and each client has relatively few mailboxes. Zoho

The architecture I'd use

For an agency, I'd separate the services:

                    ┌── VPS
yourdomain.com ─────┤   websites
                    │   applications
                    │   databases
                    │
                    └── Managed email provider
                        ├── info@domain.com
                        ├── sales@domain.com
                        ├── john@domain.com
                        └── support@domain.com

Your DNS would point MX records to the email provider, while A/AAAA records point the website to your VPS. You'd also configure SPF, DKIM and DMARC for mail.

That means you can reboot, replace, or migrate the VPS without touching everyone's email.

One important distinction

If by "email hosting" you mean normal business mailboxes (person@clientdomain.com), Migadu/Fastmail/Zoho are the sort of services I'd investigate.

If you mean agency-scale outbound/cold-email infrastructure, that's a different category. Services such as ScaledMail provision managed mailboxes, DNS authentication and sending infrastructure specifically around high-volume outbound email. ScaledMail

If you tell me roughly how many domains, total mailboxes, and whether these are your agency's domains or client domains, I can narrow this down to the 2–3 most economical setups and calculate the monthly cost.

Yes. For the setup you described—a small agency hosting multiple client domains, moving websites to a VPS but wanting email managed separately—there are several good options.

My top pick: Migadu

Migadu is unusually well suited to an agency model. It explicitly supports agencies hosting multiple client domains under one account, with unlimited addresses/mailboxes and multi-admin controls. Migadu Migadu

Current plans are account-based rather than per-mailbox:

• Mini — $9/month or $90/year
• Standard — $29/month or $290/year
• Maxi — $99/month or $990/year
• Mailboxes/addresses aren't individually billed.
• You can host multiple domains under the same account.
• Higher plans provide substantially higher sending limits and storage.
• It supports SMTP, IMAP, POP3 and webmail, so you're not locked into a proprietary mail client. Migadu Migadu

For an agency, the particularly interesting part is that Migadu has domain-level administration, mailbox limits, monitoring, and an API for creating/managing domains and mailboxes. Migadu

migadu.com

Other good choices

Microsoft Exchange Online is the better choice if your clients expect Outlook, calendars, shared mailboxes, Microsoft 365, etc. Exchange Online Plan 1 is currently $4/user/month annually and includes a 50 GB mailbox, custom domain email, spam/malware filtering, and calendar functionality. Microsoft

microsoft.com

Zoho Mail is another strong small-business option, particularly if you want conventional business email without paying for the entire Microsoft/Google productivity suite. It supports custom domains, organizational administration, and group addresses. Zoho Zoho Corporation

zoho.com

What I'd do in your situation

I'd keep mail off the VPS.

Use the VPS for:

websites → VPS

and use a dedicated mail host for:

client-domain.com → MX → mail provider

That gives you much less operational headache around spam reputation, DKIM/DMARC, IP reputation, backups, blacklists, SMTP deliverability, and mail-server maintenance.

If your agency might eventually manage 20, 50, or 100+ client domains, Migadu is particularly worth investigating because its pricing model is much more agency-friendly than paying separately for every mailbox. It even provides an API for automating domain and mailbox provisioning. Migadu Migadu

One caveat: Migadu's plans have account-level sending quotas, so I'd size the plan based on the aggregate mail volume of all your clients rather than simply counting mailboxes. Migadu

If you tell me roughly how many domains, mailboxes per domain, and total users you're expecting (e.g. 30 domains × 5 mailboxes), I can compare the economics of Migadu vs Zoho vs Microsoft 365 vs running your own mail stack on the VPS.

Yes. For a small agency moving websites from shared hosting to a VPS, I’d actually recommend keeping email off the VPS unless you specifically want to operate your own mail infrastructure.

The standout option for your use case is Migadu.

Best fit: Migadu

Migadu is unusually well suited to agencies because it lets you put multiple client domains and mailboxes under one agency account, rather than paying separately for every mailbox. It explicitly markets its service to agencies hosting clients' email domains. Migadu Migadu

For example, you could have:

• client1.com → john@client1.com, info@client1.com
• client2.com → sarah@client2.com, sales@client2.com
• client3.com → admin@client3.com, support@client3.com

all managed from one place.

Their current plans are account-based rather than per-mailbox: Mini $9/month, Standard $29/month, Maxi $99/month, with unlimited addresses and domains on the larger plans. The practical limitation is usage—sending volume and storage—not simply the number of mailboxes. Migadu

They also provide:

• IMAP/SMTP/POP3 and webmail
• Multiple administrators, including administrators restricted to particular domains
• Mailbox quotas
• Domain-health monitoring
• Backups
• API access for managing domains/mailboxes
• Standard email protocols, so you're not locked into a proprietary mail client Migadu Migadu

That domain-scoped administration is particularly useful for an agency.

migadu.com

Other options

Zoho Mail is probably my second choice if each client is more like a conventional business that needs individual users, calendars, collaboration, etc. It supports custom domains, groups such as info@, and migration from existing mail systems. Zoho Zoho Corporation

zoho.com

Fastmail is excellent for polished business email, but its pricing model is much more naturally suited to individual users/teams than an agency accumulating lots of client domains.

Self-hosted mailcow is another possibility if the goal is specifically "everything lives on our VPS." It gives you considerably more control, but email hosting is one of those services where deliverability, spam reputation, backups, IP reputation, DKIM/DMARC, monitoring, and abuse handling become your problem. I generally wouldn't put client email on the same VPS as their websites.

What I'd do for an agency

I'd use this architecture:

                 ┌── VPS
                 │    ├── Client websites
Internet ────────┤    ├── DNS/web services
                 │    └── Agency applications
                 │
                 └── Managed email provider
                      ├── client1.com
                      ├── client2.com
                      ├── client3.com
                      └── ...many domains

The VPS handles web hosting; the email provider handles mail.

Then your agency's provisioning workflow becomes:

1. Add client's domain to your email provider.
2. Create the required mailboxes/aliases.
3. Add MX records.
4. Add SPF/DKIM/DMARC.
5. Move the existing mailboxes.
6. Point the website's DNS to the VPS independently.

That separation is much safer than tying client email to the lifecycle of your VPS.

If you're expecting something like 10–50 client domains with anywhere from 2–20 mailboxes per domain, I'd strongly investigate Migadu first. Its agency/domain-based model is much closer to what you're describing than Google Workspace or Microsoft 365's per-user model. Migadu

If you tell me roughly how many domains + mailboxes you expect (e.g. 20 domains × 5 mailboxes), I can compare the actual monthly cost of Migadu vs Zoho vs Fastmail vs running mailcow on your VPS.

Self-hosted mailcow is another possibility if the goal is specifically "everything lives on our VPS." It gives you considerably more control, but email hosting is one of those services where deliverability, spam reputation, backups, IP reputation, DKIM/DMARC, monitoring, and abuse handling become your problem. I generally wouldn't put client email on the same VPS as their websites.

What I'd do for an agency

I'd use this architecture:

                 ┌── VPS
                 │    ├── Client websites
Internet ────────┤    ├── DNS/web services
                 │    └── Agency applications
                 │
                 └── Managed email provider
                      ├── client1.com
                      ├── client2.com
                      ├── client3.com
                      └── ...many domains

The VPS handles web hosting; the email provider handles mail.

Then your agency's provisioning workflow becomes:

1. Add client's domain to your email provider.
2. Create the required mailboxes/aliases.
3. Add MX records.
4. Add SPF/DKIM/DMARC.
5. Move the existing mailboxes.
6. Point the website's DNS to the VPS independently.

That separation is much safer than tying client email to the lifecycle of your VPS.

If you're expecting something like 10–50 client domains with anywhere from 2–20 mailboxes per domain, I'd strongly investigate Migadu first. Its agency/domain-based model is much closer to what you're describing than Google Workspace or Microsoft 365's per-user model.

Yes. For a small agency moving away from shared hosting + cPanel mailboxes, I would generally avoid running mail directly on your new VPS unless you specifically want to become an email administrator. Deliverability, spam reputation, backups, DKIM/DMARC, blacklists, and migrations become ongoing work.

The best options depend on whether you mean internal agency email or reselling email to clients:

1. Managed business email (best for most agencies)

workspace.google.com

• Custom domains (user@agency.com)
• Gmail interface
• Shared inbox workflows with Groups/delegation
• Excellent deliverability
• Easy migration from cPanel mail
• Scales from a few users to hundreds

Best if your agency already lives in Google Docs/Drive.

microsoft.com

• Outlook mailbox experience
• Shared mailboxes
• Teams/Office integration
• Strong admin controls

Best for agencies serving corporate clients.

zoho.com

• Lower-cost business email
• Custom domains
• Admin console
• Good fit for smaller teams

2. Email hosting platforms built around agencies/resellers

If you want to offer email as part of your hosting packages:

Atriomail

• Designed specifically for agencies and resellers
• White-label branding
• Multiple client domains
• Mailbox provisioning
• API/automation options
• IMAP migration support
• SPF/DKIM/DMARC automation Atriomail

This is closer to a replacement for "we host your website and email" packages.

MailMount

• Managed custom-domain email
• Migration assistance
• Setup support
• Team mailbox options MailMount

3. Self-hosted email on your VPS (possible, but usually not ideal)

Common stacks:

• Mailcow
• Mail-in-a-Box
• iRedMail
• Modoboa

Advantages:

• Full control
• Unlimited domains/mailboxes
• Can integrate with your hosting panel

Disadvantages:

• You own: - IP reputation
• spam filtering
• backups
• monitoring
• security updates
• blacklist removal
• outbound deliverability

A VPS IP with poor reputation can make even legitimate client email land in spam.

A practical agency architecture

A common setup is:

• VPS → websites/apps only
• Dedicated email provider → all mailboxes
• DNS → managed with Cloudflare or registrar
• Add: - SPF
• DKIM
• DMARC
• backup MX strategy

For example:

• clientsite.com hosted on your VPS
• info@clientsite.com, sales@clientsite.com hosted on Google Workspace/Zoho/Atriomail
• Your agency manages DNS and onboarding

My shortlist for a small agency

A key question: are you trying to host email only for your agency, or do you want to provide mailbox hosting as a service for your web-hosting clients? That changes the best choice quite a bit.

A key question: are you trying to host email only for your agency, or do you want to provide mailbox hosting as a service for your web-hosting clients? That changes the best choice quite a bit.

Yes. If you’re moving from shared hosting to a VPS and the agency needs to host multiple client domains with lots of domain-based mailboxes, I’d actually avoid putting mail directly on the VPS unless you specifically want to operate a mail server.

The standout option for your use case is Migadu.

Best fit: Migadu

Migadu is specifically structured around domains and addresses rather than charging you for every mailbox. Its plans allow unlimited domains and addresses, with usage limits based on the overall account. It also explicitly supports agencies hosting client domains under one account, including separate administrators and domain/mailbox limits. Migadu Migadu

Current plans include:

• Micro: $19/year, 5 GB
• Mini: $9/month or $90/year, 30 GB
• Standard: $29/month or $290/year, 100 GB
• Maxi: $99/month or $990/year, 500 GB

The important distinction is that these are account-level prices, not per-mailbox prices. Migadu

So, for example, if you have:

client-a.com
  john@
  jane@
  info@
  support@

client-b.com
  bob@
  info@
  billing@

client-c.com
  alice@
  support@

you aren't buying 10 individual mailbox subscriptions.

Migadu also gives you standard SMTP/IMAP/POP3/webmail, aliases, SIEVE filtering, backups, domain-health monitoring, and multi-admin capabilities. Migadu

Other options I'd consider

Zoho is particularly inexpensive for conventional mailbox-per-user setups; its Mail Lite pricing starts around $1/user/month, while higher tiers add more administration and storage capabilities. Zoho

One other interesting option: self-hosted

If your real goal is "we're moving everything onto our VPS and want email to be another service we control," there are newer products aimed exactly at that. For example, Vectis Mail describes itself as a self-hosted alternative with flat-rate, domain-unlimited pricing, REST API access, inbound webhooks, and VPS ownership. Vectis Mail

But I'd be cautious here. Running mail yourself means you're responsible for:

• IP reputation
• SPF/DKIM/DMARC
• reverse DNS
• spam filtering
• blocklists
• backups
• queue management
• TLS
• mailbox security
• deliverability troubleshooting

A VPS that works perfectly for websites can be terrible for outbound email because the VPS provider's IP ranges may already have reputation problems.

What I'd do for a small agency

I'd separate web hosting and email hosting:

                    ┌── VPS
                    │
client-a.com ───────┤   Website
client-b.com ───────┤   Website
client-c.com ───────┤   Applications
                    │
                    └── DNS
                         │
                         ▼
                    Email provider
                    ├── client-a.com
                    ├── client-b.com
                    ├── client-c.com
                    └── all mailboxes

That gives you the VPS freedom you're looking for without turning your agency into an email-delivery company.

For an agency with many small client domains, I'd investigate Migadu first. Its pricing model is unusually well aligned with the agency model because adding another info@, support@, or client domain doesn't automatically create another per-user bill. Migadu

migadu.com

If you tell me roughly how many domains + total mailboxes you're expecting (e.g. 30 domains / 150 mailboxes), I can compare the actual monthly cost of Migadu vs Zoho vs Microsoft 365 vs self-hosting and tell you which architecture makes the most sense.

Yes. For a small agency moving websites from shared hosting to a VPS, I’d generally recommend not hosting the mailboxes on the VPS itself. Keep the VPS focused on web/app hosting and use a dedicated email provider for deliverability, spam filtering, backups, and mailbox management.

A few good fits:

My first choice: Fastmail

Fastmail Business is particularly interesting for an agency because it supports multiple domains in one account, individual mailboxes, aliases such as info@, sales@, and support@, and migration from an existing mail host. Fastmail says an account can have up to 100 domains, which is useful if you're managing mail for multiple clients. www.fastmail.com

It also means your architecture becomes:

Client domain → MX records → Fastmail → mailboxes

while:

Client domain → A/AAAA records → your VPS → website

So moving a client's website between servers doesn't require moving their email.

Fastmail's business plans are currently roughly $4–$10/user/month, depending on storage/features, with the middle tier providing 50 GB/user and custom domains. www.fastmail.help

Zoho is worth looking at too

Zoho Mail is probably the other one I'd investigate seriously for an agency. It supports custom domains, mailbox creation, distribution/group addresses, and migration from existing providers. www.zoho.com

Zoho is particularly attractive if your typical client has something like:

• 3–15 actual users
• info@, sales@, etc.
• relatively modest mailbox storage requirements
• a strong preference for keeping costs down

One important distinction

If by "scalable email hosting" you mean normal business mailboxes—people using Outlook, Apple Mail, Gmail apps, webmail, etc.—I'd look at Fastmail/Zoho/Google/Microsoft.

If you mean high-volume outbound email, cold outreach, or marketing mail, that's a different category. For example, ScaledMail sells managed mailbox infrastructure specifically for high-volume/cold-email sending, with DNS authentication and mailbox provisioning. www.scaledmail.com I wouldn't use that as the normal mailbox host for agency clients.

What I'd build for an agency

I'd actually consider making email hosting a separate service from the VPS hosting:

                 ┌── VPS / Web Hosting
Client Domain ──┤
                 └── Email Provider
                       ├── user@domain.com
                       ├── info@domain.com
                       └── support@domain.com

Then your agency can provision a new client by:

1. Add their domain to your email platform.
2. Create their users/mailboxes.
3. Set MX, SPF, DKIM and DMARC.
4. Migrate their existing mail.
5. Point their website DNS at your VPS.
6. Keep email completely independent of the VPS.

That gives you a much cleaner setup than running Postfix/Dovecot/etc. for every client yourself.

If you tell me roughly how many domains and mailboxes you're expecting (e.g. 20 clients × 5 mailboxes each), I can compare the actual monthly cost of Fastmail vs Zoho vs Google Workspace vs self-hosting mail on the VPS and recommend an agency architecture.

Yes. For a small agency moving away from shared hosting, you generally do not want to run mailboxes directly on your VPS unless you specifically want to become an email administrator. Deliverability, spam filtering, reputation management, backups, DKIM/SPF/DMARC, and abuse handling are much harder than hosting websites.

The right tool depends on whether you are:

1. Hosting your own agency mail only
2. Managing email for many client domains
3. Reselling email as part of your hosting package

Good options for an agency

If you are becoming a hosting provider for clients

Look for a platform with:

• Unlimited domains
• Unlimited aliases/forwarders
• Per-mailbox billing
• Client isolation
• White-label webmail
• API provisioning
• WHMCS/Blesta integration
• Automatic SPF/DKIM/DMARC setup
• IMAP migration tools

A platform like Atriomail is aimed specifically at agencies/hosts that want to sell email under their own brand. atriomail.com

If you are moving from cPanel shared hosting

A common architecture is:

VPS
 ├── Websites
 ├── Databases
 └── Apps

External Email Provider
 ├── clientdomain.com
 │    ├── info@
 │    ├── sales@
 │    └── staff@
 ├── anotherclient.com
 │    └── support@

Your DNS points:

• A records → your VPS
• MX records → email provider
• SPF/DKIM/DMARC → email provider

This keeps website outages separate from email outages.

For a small agency, I would usually choose:

• 5–50 internal mailboxes: Google Workspace, Microsoft 365, or Zoho Mail
• 50–500 client mailboxes: Atriomail, a white-label provider, or a managed mail platform
• Want maximum control: VPS + a mail stack like Mailcow, but only if you are comfortable operating email infrastructure

A useful question: are you trying to host your agency’s own email, or do you want to offer email hosting to your web-hosting clients as a service? The best choice changes quite a bit.

Yes. For a small agency moving away from shared hosting, you generally do not want to run mailboxes on your VPS unless you specifically want to become an email administrator. Self-hosted email brings deliverability, spam filtering, reputation, backups, DKIM/SPF/DMARC, and blacklist monitoring headaches.

The better options depend on whether you need internal agency mail only or you want to resell email to clients.

Good managed email hosting options

If you are an agency hosting client websites

I would look at a mail reseller/white-label platform rather than normal business email:

• You keep your VPS for websites/apps.
• Email lives on a dedicated mail platform.
• You can create:
  • clientname.com
  • info@clientname.com
  • support@clientname.com
  • staff mailboxes
• You manage DNS and accounts from one panel.
• You can optionally bill clients for email.

Platforms such as Atriomail specifically target agencies and resellers with white-label branding, mailbox provisioning, migration tools, and DNS automation. atriomail.com

If you only need your own agency email

A common setup:

• VPS → websites, apps, client portals
• Cloudflare → DNS
• Email provider → mailboxes

Example:

VPS
 ├── agencywebsite.com
 ├── client1website.com
 └── client2website.com

Email provider
 ├── hello@agency.com
 ├── billing@agency.com
 ├── client1.com mailboxes
 └── client2.com mailboxes

Features I would require before choosing one

For an agency, make sure it supports:

✅ Multiple domains
✅ Unlimited aliases/forwarders
✅ IMAP/SMTP
✅ Webmail
✅ SPF + DKIM + DMARC management
✅ Mailbox migration tools
✅ Catch-all addresses (optional but useful)
✅ Admin API or automation (important as you grow)
✅ Good outbound reputation

Avoid cheap shared-hosting mailboxes for client-facing businesses; they often share IP reputation with many unrelated senders.

If you are moving from cPanel shared hosting and want something like "create email accounts per client domain from one dashboard", I would specifically compare Atriomail, MXroute, Mailcow (self-hosted), and Zoho Mail. www.dreamhost.comatriomail.com

Yes. In fact, for a small agency moving websites from shared hosting to a VPS, I’d generally keep email off the VPS and use a dedicated hosted email provider. It avoids deliverability, spam reputation, backups, blacklists, and mail-server maintenance becoming your problem.

For an agency managing multiple client domains, these are particularly worth looking at:

My first choice for an agency: Migadu

Migadu is unusually well suited to the model you're describing.

It explicitly supports agencies hosting clients' email domains under one account, with multiple domains, multiple administrators, domain-level access controls, and unlimited mailboxes/addresses. Its pricing is based on account usage rather than charging separately for every mailbox. www.migadu.commigadu.com

For example, you could have:

Agency Migadu account
│
├── client-a.com
│   ├── john@
│   ├── jane@
│   ├── sales@
│   └── support@
│
├── client-b.com
│   ├── alice@
│   ├── info@
│   └── billing@
│
└── client-c.com
    ├── bob@
    └── contact@

That is much more attractive than paying for a separate email subscription for every address.

Migadu's current plans include unlimited domains and addresses, with the higher tiers increasing daily sending/receiving quotas and storage. The current Standard plan is listed at $29/month and Maxi at $99/month. www.migadu.com

Fastmail is another strong option

Fastmail Business is probably the option I'd choose if user experience and polished administration matter more than minimizing mailbox costs.

Fastmail supports custom domains, shared addresses such as support@, multiple domains, migration from existing providers, and third-party clients such as Outlook and Thunderbird. It currently supports up to 100 domains on an account. www.fastmail.com

The downside for an agency is that you're generally paying based on users/mailboxes rather than getting Migadu's "lots of mailboxes under one account" economics.

Zoho is worth considering

Zoho Mail is another good middle ground. It supports custom domains, migration from existing mail systems, aliases, centralized administration, and multiple domains. Paid organizations can currently have up to 30 domains. www.zoho.com

It's particularly interesting if your clients want more of a traditional business-email suite rather than simply IMAP/SMTP mail hosting.

What I'd do in your situation

If you're an agency and the model is:

"We host 10–100+ client websites on our VPS infrastructure, and each client may have 1–20 domain mailboxes."

I'd seriously investigate Migadu first.

The architecture becomes:

VPS
→ websites, databases, DNS management, backups, etc.

Dedicated email provider
→ MX records, mailboxes, spam filtering, SMTP/IMAP, mail reputation, backups

That separation is much safer than running Postfix/Dovecot/etc. yourself on the VPS.

One particularly nice feature for an agency is that Migadu lets you set limits at the domain/mailbox level and monitor domain health, so one client's email usage doesn't necessarily become an uncontrolled resource problem for everyone else. www.migadu.commigadu.com

If you tell me roughly how many client domains, mailboxes per domain, and total monthly email volume you're expecting, I can compare Migadu vs Fastmail vs Zoho and work out which would be cheapest at your scale.

Yes. For a small agency moving websites from shared hosting to a VPS, I’d keep email off the VPS and use a dedicated hosted email provider. It gives you much better deliverability, spam filtering, backups, and less operational headache.

My first choice: Migadu

Migadu is particularly well suited to an agency that manages multiple client domains.

• Unlimited domains and email addresses on its paid plans; pricing is based on account usage rather than charging for every mailbox. migadu.commigadu.com
• Explicitly supports agencies hosting clients' domains under one account. www.migadu.com
• Supports normal IMAP, SMTP, POP3 and webmail, so clients can use Outlook, Apple Mail, Thunderbird, etc. migadu.commigadu.com
• Has an API for managing domains and mailboxes, which is interesting if you eventually want your VPS/client-management system to provision mailboxes automatically. www.migadu.comwww.migadu.com
• Current plans include roughly $9/month for Mini, $29/month for Standard, and $99/month for Maxi, with different usage/storage limits. migadu.com

That pricing model is unusually attractive if you have, say, 30 client domains but only 80 actual users. You aren't multiplying a per-mailbox price across every address.

Other good choices

Zoho Mail — probably my second choice if you want a more conventional business-email platform. It supports custom domains, user/group addresses, and migration from an existing provider. www.zoho.com

Zoho Mail pricing

Microsoft 365 / Exchange Online — excellent if your clients live in Outlook/Office/Teams, but it's fundamentally a per-user model. Exchange Online starts at $4/user/month annually, while Business Basic is currently $4.40/user/month without Teams. www.microsoft.com

Microsoft 365 Business Email

Fastmail — very good email product and has custom domains, shared addresses, admin controls, and migration tools, but again tends to make more sense when you're managing a company's users rather than dozens of unrelated client domains. www.fastmail.com

Fastmail Business

For your particular setup

I'd architect it roughly like this:

VPS
→ websites
→ databases
→ DNS automation / client portal
→ backups

Dedicated email provider
→ client1.com
→ client2.com
→ client3.com
→ etc.

DNS
→ MX → email provider
→ SPF → email provider
→ DKIM → email provider
→ DMARC → your policy/reporting

That way, if the VPS gets rebooted, compromised, overloaded, or you migrate to another VPS, your clients' email keeps working independently.

If you're looking for something that behaves almost like “cPanel email hosting, but centralized across all my agency clients”, Migadu is the one I'd investigate first. It even has the API/admin structure to make agency-scale provisioning practical. www.migadu.comwww.migadu.com

If you tell me roughly how many domains, mailboxes, aliases/forwarders, and GB of mail you expect (e.g. 25 domains / 100 mailboxes / 300 aliases), I can compare the likely monthly cost of Migadu vs Zoho vs Microsoft 365 and tell you which model makes the most sense.

Yes. If you're moving from shared hosting to a VPS, I’d actually recommend not hosting the mailboxes on the VPS itself unless you specifically want to operate a mail server. Keeping email with a dedicated provider gives you better deliverability, backups, spam filtering, and less operational risk.

For a small agency with multiple client domains, these are worth looking at:

I'd look at Migadu first

Migadu is unusual because it is designed around the domain rather than simply charging for every mailbox. It supports multiple domains, aliases, catch-alls, standard IMAP/SMTP, and domain aliases. www.migadu.com

That makes it attractive if, for example, your agency has:

• 10 client domains
• 30–50 actual mailboxes
• addresses like info@, sales@, support@, etc.
• lots of aliases/forwarding addresses
• clients coming and going

Instead of running Postfix/Dovecot/Rspamd/etc. on your VPS, you point each domain's MX records at the email provider and let your VPS concentrate on websites/apps.

If you need shared team inboxes

I'd also investigate Shipmail. It's specifically positioning itself around agencies with multiple domains and shared addresses, including scenarios where several team members need access to things like support@clientA.com without sharing passwords. shipmail.to

That's a different use case from simply having 30 independent mailboxes.

Fastmail is another very solid option

Fastmail supports custom domains and has a straightforward migration process where you can configure the new users before switching MX records, which makes a shared-host-to-new-provider migration relatively painless. www.fastmail.help

Its business plans are priced per user, currently ranging from $4/user/month for Business Basic to $10/user/month for Professional. www.fastmail.help

For your particular architecture, I'd probably do:

Registrar/DNS → email provider → mailboxes
** ↘ VPS → websites/apps/databases**

rather than:

Registrar/DNS → VPS → self-hosted mail server

The latter is certainly possible, but email deliverability becomes an ongoing infrastructure responsibility—SPF, DKIM, DMARC, reverse DNS, IP reputation, blocklists, spam filtering, backups, abuse handling, etc.

If you tell me roughly how many domains, mailboxes, aliases, and users your agency has now (and what you expect in 1–3 years), I can compare the economics of Migadu vs Zoho vs Fastmail vs Google Workspace vs Shipmail for your specific setup.

Yes. In fact, I’d generally recommend keeping mail off the VPS and using a dedicated hosted email provider. Your VPS can run the agency’s websites/apps while a specialized mail provider handles deliverability, spam filtering, backups, and mailbox scaling.

A few good fits:

For an agency, I'd look closely at Migadu

The important distinction is that you probably don't want a provider that makes you buy a separate expensive "workspace" for every domain.

If your agency manages something like:

• agency.com
• clientone.com
• clienttwo.com
• clientthree.com

and you need:

• info@clientone.com
• support@clientone.com
• john@clientone.com
• info@clienttwo.com
• etc.

then domain/alias/mailbox architecture and pricing matter much more than raw mailbox storage.

Zoho is another very strong choice

Zoho explicitly supports adding your own domains, creating multiple users, aliases and group addresses, and migrating existing mailboxes. Its current paid plans can scale to any number of user accounts. www.zoho.com

For example, its current pricing shows Mail Lite at $1/user/month for 5 GB or $1.25/user/month for 10 GB when billed annually, with higher tiers available. www.zoho.comwww.zoho.com

It also provides a migration tool and supports SPF/DKIM/DMARC configuration, which is important when moving away from shared hosting. www.zoho.comwww.zoho.com

One architecture I'd recommend

                    ┌── VPS ── Websites
Internet ── DNS ────┤
                    ├── VPS ── Apps / databases
                    │
                    └── Email provider
                           ├── agency.com
                           ├── client1.com
                           ├── client2.com
                           └── client3.com

Your domains' A/AAAA records can point websites to the VPS, while their MX records point to the email provider.

That gives you a nice separation:

VPS: websites, applications, databases
Email provider: SMTP, IMAP, webmail, spam filtering, mailbox storage, deliverability

I would not put Postfix/Dovecot directly on the VPS unless you specifically want to become your own mail administrator. Running mail reliably is considerably more involved than running websites, particularly with IP reputation, spam, DKIM, DMARC, reverse DNS, blacklists, backups, and deliverability.

If you tell me roughly how many domains you manage, how many actual users/mailboxes per domain, and whether these are your agency's domains or client domains, I can narrow this down to the 2–3 providers whose pricing model makes the most sense for an agency.

Yes. If by “scalable” you mean multiple client domains + lots of domain-based mailboxes/aliases without having to run mail infrastructure on the VPS, there are several good options.

My shortlist

Migadu is probably the one I'd investigate first for your particular scenario. It explicitly targets web agencies and supports unlimited domains and email addresses, multi-admin access with domain-level permissions, aliases, standard SMTP/IMAP/POP3, backups, and mailbox quotas. That makes it much more aligned with an agency that might go from, say, 5 domains/30 mailboxes to 50 domains/300 mailboxes without wanting to administer a mail server. www.migadu.com

Zoho Mail is the safer mainstream choice if you want a polished business-email product. You can add domains, create individual mailboxes and groups, use aliases, and migrate existing IMAP/POP mail. www.zoho.com

Fastmail is particularly nice if these are primarily your agency's own employees rather than dozens of clients. Its business plans support custom domains, shared addresses such as support@, admin controls, and migration tooling. www.fastmail.com

One important architectural point

I wouldn't put your production email server on the new VPS just because you're moving the websites there.

A good architecture would be:

                    ┌── VPS
DNS ────────────────┤
                    │   websites / apps / databases
                    │
                    └── Email provider
                         ├── client1.com
                         │    ├── john@
                         │    ├── billing@
                         │    └── support@
                         ├── client2.com
                         └── client3.com

The VPS handles web hosting, while the email provider handles MX, spam filtering, DKIM/SPF/DMARC, mailbox storage, backups, reputation, and mail delivery.

That's especially valuable for an agency: one misconfigured VPS, compromised WordPress site, or bad outbound mail campaign shouldn't jeopardize email delivery for every client domain.

If you tell me roughly how many domains and mailboxes you expect (e.g. 20 domains / 100 mailboxes) and whether these are your agency's users or mailboxes for your clients, I can narrow this down to the 2–3 best options and compare the likely monthly cost.

Yes. If you're moving from shared hosting mail to a VPS for the websites, I would generally keep email separate from the VPS. Running your own mail server is possible, but deliverability, spam reputation, backups, DNS authentication, and IP reputation make it much more operationally expensive than it first appears.

For a small agency handling multiple client domains and domain-based mailboxes, a few options stand out:

My first choice for an agency: Shipmail

This is particularly interesting for your use case because its pricing is based on mailboxes rather than users or domains. It currently supports up to 50 custom domains per organization, with plans from 2–12 mailboxes and a Scale tier from 13–300 mailboxes. Shared inbox functionality is built in. shipmail.to

So you could have something like:

• hello@agency.com
• billing@agency.com
• support@client-a.com
• info@client-b.com
• admin@client-c.com

…and manage the domains centrally rather than maintaining separate email installations for every client.

That's a particularly good model if your agency is actually hosting/managing email for clients, rather than merely needing email for your own staff.

Migadu is worth a serious look

If your main requirement is lots of domains + lots of basic mailboxes, Migadu is compelling. It supports domain aliases and is designed around managing multiple domains from one account. www.migadu.com

I'd lean toward Migadu if you want:

"Give me a centralized place to host 30–100 relatively ordinary client mailboxes as cheaply as possible."

I'd lean toward Shipmail if you want:

"Give my agency a centralized email platform where multiple staff can work with client inboxes."

Zoho is the more conventional business choice

Zoho Mail is also very suitable. Its administration supports custom domains, user/mailbox creation, groups, aliases, SPF/DKIM configuration, and migration from existing providers. www.zoho.com

It's probably the safer choice if your clients expect something resembling a traditional business-email service rather than an agency-oriented platform.

I would not put email on the VPS by default

If you're moving:

cPanel/shared hosting → VPS

I'd structure it as:

                    ┌── VPS
                    │   ├── Websites
                    │   ├── Databases
                    │   └── Apps
                    │
Domains ────────────┤
                    │
                    └── Managed Email Provider
                        ├── client-a.com
                        ├── client-b.com
                        ├── client-c.com
                        └── agency.com

Your VPS then isn't responsible for SMTP reputation, spam filtering, mailbox storage, IMAP, DKIM signing, mail queues, etc.

You simply point each domain's MX records at the email provider and configure SPF/DKIM/DMARC.

If you tell me roughly how many client domains and mailboxes you're talking about (e.g. 20 domains / 100 mailboxes), I can compare the actual economics of Shipmail vs Migadu vs Zoho vs self-hosted Mailcow and tell you which architecture I'd use for an agency.

Yes. If the agency is moving web hosting to a VPS but doesn't want to operate its own mail server, I'd strongly recommend keeping email on a dedicated hosted-email provider. That gives you better deliverability, spam filtering, backups, and less maintenance than running Postfix/Dovecot yourself.

For an agency that may host multiple client domains, one option stands out:

1. Migadu — probably the best fit

Migadu

Migadu is specifically designed around multiple domains and large numbers of addresses rather than charging you strictly per mailbox. Its current plans allow unlimited addresses and domains, with the account's overall mail volume/storage determining the tier. The Maxi plan is currently $99/month, Standard $29/month, and Mini $9/month. www.migadu.comwww.migadu.com

For an agency, the particularly useful features are:

• Multiple client domains under one account
• Unlimited mailboxes/addresses within plan limits
• Multiple administrators with domain-level restrictions
• Per-mailbox/domain quotas
• Domain-health monitoring
• Standard SMTP/IMAP/POP3
• Aliases and catch-all addresses
• Backups
• No proprietary mail client lock-in www.migadu.comwww.migadu.com

That makes it unusually well suited to a setup like:

Agency
├── client-a.com
│   ├── john@
│   ├── jane@
│   └── info@
├── client-b.com
│   ├── sales@
│   └── support@
└── client-c.com
    ├── admin@
    └── billing@

You can keep all of those domains managed centrally while the VPS handles websites/applications only.

2. Zoho Mail — better if you want a formal reseller model

Zoho Mail Partnership

Zoho is interesting if the agency intends to sell email hosting to clients as a service. Its partnership program provides centralized management of multiple customer organizations, migration tools, partner management, and reseller capabilities. It also supports WHMCS integration. www.zoho.com

That's a stronger choice if your business model is:

"We host your website and also sell/manage your business email."

rather than simply:

"We need email for our own agency."

3. Fastmail — excellent email, less agency-oriented

Fastmail Business

Fastmail is a very good choice for a single organization. It supports custom domains, shared addresses such as support@, centralized administration, IMAP/SMTP, and migration assistance. www.fastmail.com

But if you're going to have dozens of unrelated client domains, I'd put Migadu or Zoho ahead of it.

What I would do in your situation

If the agency is moving from cPanel/shared hosting → VPS, I'd separate the infrastructure:

VPS

• Websites
• WordPress
• Databases
• APIs
• Cron jobs
• DNS if desired

Hosted email

• MX records point to provider
• Mailboxes live entirely outside the VPS
• SPF/DKIM/DMARC configured
• Webmail/IMAP/SMTP handled by provider
• Backups and spam filtering handled by provider

That way, a VPS reboot, migration, compromise, or web-server outage doesn't take down everyone's email.

My shortlist would be:

One important distinction: if by "scalable email hosting" you mean normal business mailboxes, Migadu/Zoho are appropriate. If you mean high-volume outbound/marketing/cold email, that's a different infrastructure problem; you shouldn't use ordinary employee mailboxes for that.

If you tell me roughly how many domains and mailboxes you expect (e.g. 20 domains / 150 mailboxes), I can compare the actual monthly cost and recommend the most economical architecture.

Yes. If you're moving the website/app hosting to a VPS, I’d generally keep email separate rather than running mailboxes on the VPS. That gives you better deliverability, backups, spam filtering, and much less operational headache.

For a small agency, there are a few good models:

My pick for an agency

If you mean "we're an agency and will potentially host email for multiple client domains", I'd look particularly closely at Atriomail.

It is explicitly designed for resellers and agencies, with white-label branding, automatic DNS management, API/control-panel integrations, unlimited domains/aliases/forwarders, and IMAP migration. Its advertised pricing starts around $1.39/mailbox/month, with 15 GB included. atriomail.com

That's quite different from Google Workspace/Microsoft 365, where you're essentially buying a productivity-suite account for every user.

If you're just looking for email for your agency itself, then Google Workspace is the safer mainstream choice. Business Starter currently supports custom-domain email and is $7/user/month with an annual commitment ($8.40 monthly), with 30 GB pooled storage per user. knowledge.workspace.google.com

Microsoft 365 is similarly strong if your clients/users live in Outlook/Office. Business plans support custom domains and 50 GB Exchange mailboxes. atriomail.comsupport.microsoft.com

One important distinction

If your agency needs something like:

Client A → 8 mailboxes
Client B → 3 mailboxes
Client C → 20 mailboxes
Client D → 2 mailboxes

…and you want to manage all of those from one agency account/control panel, don't automatically choose Google Workspace or Microsoft 365. Look at an email hosting/reseller platform such as Atriomail or similar.

If you tell me roughly how many client domains + total mailboxes you're expecting (e.g. 20 domains / 100 mailboxes), I can compare the current providers by cost, mailbox limits, storage, migration, white-labeling, APIs, and deliverability and tell you which architecture makes the most sense.

Yes. If you're moving websites from shared hosting to a VPS but don't want to run mail yourself, I'd strongly consider keeping email as a separate hosted service. That gives you VPS flexibility without taking on the deliverability, spam, DKIM/DMARC, backups, and reputation problems of self-hosting mail.

Good fits for a small agency

Zoho Mail is probably the first one I'd investigate for your use case. It supports custom domain mailboxes, groups, aliases, domain administration, and migration from existing IMAP/POP mail systems. help.zoho.com

For an agency, the important distinction is mailboxes vs. domains. If you have, say:

• 20 client domains
• 3–10 mailboxes per domain
• aliases such as info@, sales@, support@
• centralized administration

you want a provider whose pricing doesn't punish you simply for having many domains.

I'd architect it like this

VPS

• Nginx/Apache
• PHP/Node/etc.
• client websites
• databases
• automated backups

Hosted email provider

• alice@client1.com
• bob@client1.com
• info@client2.com
• etc.

DNS

• A/AAAA → VPS
• MX → email provider
• SPF → email provider
• DKIM → email provider
• DMARC → your chosen policy

This is much cleaner than running Postfix/Dovecot on the VPS. Your VPS can even be replaced without affecting mail.

Zoho specifically supports adding multiple domains, creating users/groups, aliases, and migrating existing mailboxes via IMAP. help.zoho.com

If you're looking for something that you can resell/manage for multiple agency clients, though, I'd narrow the choice differently. The key question is whether you want one agency-level account managing many client domains, or a separate email account/tenant for each client. If you tell me roughly how many domains and mailboxes you expect (e.g. 20 domains × 5 mailboxes), I can compare the best options and their current pricing.

Yes. If you're moving the websites to your own VPS but don't want to run mail servers yourself, there are several good options. For a small agency, I’d generally keep web hosting and email hosting separate.

Best fits

The interesting one for an agency: Shipmail

If by "agency" you mean you're hosting email for multiple clients/domains, rather than just your own agency domain, I'd look particularly closely at Shipmail. It is explicitly designed around agencies with multiple domains and role/shared inboxes, and its model is based on mailboxes rather than forcing every person into a full productivity suite. shipmail.to

For example, you could potentially have:

client-a.com
  alice@client-a.com
  support@client-a.com

client-b.com
  bob@client-b.com
  hello@client-b.com

youragency.com
  you@youragency.com
  support@youragency.com

without tying email to the VPS running the websites.

If it's only your agency's email

I'd lean toward Fastmail or Zoho Mail.

Fastmail is particularly clean if you want "email hosting as infrastructure": custom domains, multiple users, shared addresses such as support@, third-party clients like Outlook/Apple Mail, and migration tooling. www.fastmail.com

Zoho is worth considering if cost per mailbox is the priority. It supports multiple accounts on a domain, groups/distribution addresses, and migration from an existing provider. It also has a small free tier for up to five users on one domain, although the free tier lacks IMAP/POP/ActiveSync. www.zoho.com

One important architectural point

I wouldn't run Postfix/Dovecot on the VPS just because you're moving away from shared hosting.

Running your own mail server means taking responsibility for:

• spam filtering
• DKIM/SPF/DMARC
• IP reputation
• blacklists
• backups
• mailbox storage
• malware scanning
• TLS
• outbound deliverability
• monitoring and abuse handling

The VPS can remain responsible for websites, databases, APIs, etc., while your MX records point to a dedicated email provider.

If you tell me roughly how many domains and mailboxes you need now (e.g. 10 domains / 40 mailboxes), whether they're all yours or client domains, and your approximate monthly budget, I can narrow this down to the 2–3 best architectures and compare the actual costs.

Yes. In fact, for a small agency moving websites from shared hosting to a VPS, I’d generally recommend not hosting email on the VPS. Keep the VPS for websites/apps and put email with a dedicated mail provider. That avoids deliverability, spam reputation, backups, IP reputation, and mail-server maintenance becoming your problem.

For an agency that may manage multiple client domains and domain-based mailboxes, these are worth looking at:

My first choice: MXroute

If your agency might have something like:

• 10 client domains
• 30–100 total mailboxes
• info@, sales@, support@, etc.
• relatively modest storage requirements

MXroute is unusually well suited to that model. Its current plans advertise unlimited domains and unlimited accounts, with the Small plan at $59/year for 10 GB and higher tiers at $69/year for 25 GB and $79/year for 50 GB. It supports IMAP/SMTP/POP3. mxroute.com

It also has reseller plans, which could be particularly interesting if you're actually providing email hosting as part of your agency's service. The reseller offering includes a white-label control panel, customer logins, your branding, and your own pricing while MXroute operates the infrastructure. mxroute.com

Fastmail is nicer if mailbox quality matters more

Fastmail is a better choice if you're talking about a smaller number of users who want a really good email experience rather than maximizing mailbox count.

It supports custom domains, shared addresses such as support@, multiple domains, migration from an existing provider, and standard email clients such as Outlook and Thunderbird. Fastmail currently allows up to 100 domains in an account. www.fastmail.comwww.zoho.com

Zoho is the inexpensive "business email" option

Zoho is worth considering if you want something that feels more like traditional business email administration. Its admin console supports multiple domains, users, groups, aliases, migration, SPF/DKIM, and MX configuration. www.zoho.com

It also has a free tier for one domain and up to five users, although the free tier has limitations such as no IMAP/POP/ActiveSync. www.zoho.com

Shipmail is interesting specifically for agencies

This is one I'd investigate if your agency manages email for clients, rather than merely needing email for your own employees. Its agency offering is explicitly built around multiple client domains, shared/role-based inboxes, and adding/removing client domains. shipmail.to

The architecture I'd recommend

Rather than:

VPS → Postfix/Dovecot → all client mail

I'd do:

Domains/DNS
↓
Dedicated email provider
↓
user@client1.com
info@client1.com
user@client2.com
support@client2.com

and separately:

VPS
↓
Client websites / WordPress / apps / databases

Then configure each domain's MX, SPF, DKIM and DMARC records to the email provider.

That gives you the ability to move a client's website between servers without touching their email infrastructure.

If you're expecting a lot of client domains and mailboxes, I'd shortlist MXroute and Shipmail first. If it's only your agency's own 5–20 users, I'd lean Fastmail or Zoho.

If you tell me roughly how many domains + mailboxes you expect (e.g. 20 domains / 100 mailboxes) and whether you need to resell/white-label the email to clients, I can narrow this down to the best 2–3 options and compare the actual monthly/annual cost.