ChatGPT answers, unedited

If you’re an agency evaluating a platform before moving client lists, I’d prioritize tools that let you:

• create a sandbox account without payment,
• import a sample/client list safely,
• test segmentation, automations, reporting, integrations, and permissions,
• export your data if it doesn’t fit.

The best “free forever” candidates depend on what you’re migrating from/to (CRM, email marketing, marketing automation, client portal, etc.), but these are strong testing options:

My shortlist for an agency migration test

If you manage client marketing/email lists

1. Brevo — easiest “import a copy of a list and see if workflows fit” test.
2. GetResponse — better if you need funnels, landing pages, and automation evaluation. GetResponse
3. Mautic/self-hosted options — best if avoiding per-contact pricing matters.

If you’re replacing a CRM

1. HubSpot Free CRM — good for proving adoption with a few clients before committing.
2. Capsule CRM — simpler pilot environment with fewer moving parts. Capsule CRM

Agency migration approach I’d use

1. Export one small client list (e.g., 500–2,000 contacts, depending on size).
2. Import into the free account.
3. Recreate: - 2–3 segments,
4. one nurture sequence,
5. one campaign,
6. one reporting dashboard,
7. one integration.
8. Test: - unsubscribe handling,
9. duplicate detection,
10. tags/custom fields,
11. team permissions,
12. client approval workflow.
13. Only then migrate the full database.

A key agency concern: avoid migrating your entire client database into a platform that charges by contacts before you’ve validated the workflow. Some tools are “free” for testing but become expensive once multiple client lists are active. GetResponse

If you tell me what you’re migrating from (Mailchimp, HubSpot, ActiveCampaign, GoHighLevel, Salesforce, etc.) and whether you need white-label/client workspaces, I can narrow this to the best 3–5 options.

If you’re evaluating CRM/client-management platforms for an agency, I’d prioritize free-forever tiers where you can actually import a representative client dataset and exercise the workflows—not just a 14-day trial.

My shortlist for an agency

1. HubSpot — start here.
HubSpot currently advertises a no-cost CRM with core CRM functionality and no expiration. Its official pages describe contact/deal/task management, email tracking, meeting scheduling and other useful testing capabilities. HubSpot HubSpot

One caveat: HubSpot's own pages currently give inconsistent free-tier limits—some say up to 1 million contacts/unlimited users, while its pricing page says the free tools are for up to 2 users and another FAQ says 1,000 contacts. HubSpot HubSpot I'd therefore verify the limits displayed for your account before loading a large client list.

hubspot.com

2. Zoho CRM — best second test.
It's particularly useful if you want to compare a more conventional CRM architecture against HubSpot. Current 2026 comparisons put its free tier at up to 3 users and around 5,000 records, with leads, contacts, accounts and deals. Dupple Sasanova

zoho.com

3. Bitrix24 — test if your agency needs collaboration too.
Its official site currently describes the free CRM as $0 forever, with unlimited contacts, deal pipelines, email campaigns and team communication, and specifically supports CSV import with field mapping and deduplication. Bitrix24

bitrix24.com

How I'd run the evaluation

Don't migrate the real client database yet. Create a synthetic/test copy containing ~100–500 representative records and test:

• CSV import + field mapping
• Duplicate detection
• Custom fields
• Companies/accounts vs. individual contacts
• Multiple pipelines/client types
• User permissions
• Email/calendar integration
• Tasks and follow-ups
• Automation triggers
• Reporting
• Exporting the data back out
• API/integration availability
• What happens when you hit the free-tier ceiling

The export test is especially important for an agency: a platform that makes importing easy but makes clean data extraction difficult can create a painful future migration.

If you're choosing between HubSpot, Zoho, Bitrix24, and another specific platform, I can also give you an agency-focused migration test matrix showing exactly what to test before entrusting it with client lists.

hubspot.com

2. Zoho CRM — best second test.
It's particularly useful if you want to compare a more conventional CRM architecture against HubSpot. Current 2026 comparisons put its free tier at up to 3 users and around 5,000 records, with leads, contacts, accounts and deals. Dupple Sasanova

zoho.com

3. Bitrix24 — test if your agency needs collaboration too.
Its official site currently describes the free CRM as $0 forever, with unlimited contacts, deal pipelines, email campaigns and team communication, and specifically supports CSV import with field mapping and deduplication. bitrix24.com

If you mean CRM/client-management platforms with a genuinely free-forever tier—so an agency can build a sandbox, import a representative client list, and test workflows before committing—these are the ones I’d shortlist in 2026:

HubSpot is particularly attractive for an agency doing a low-risk migration pilot: its current materials advertise a free tier, no credit card requirement, and up to 1 million contacts, although HubSpot's pricing/help pages have some inconsistencies about the exact free-user/contact limits, so I'd verify the limits in the account you're creating before loading a production list. www.hubspot.com

Zoho is probably the better structured CRM test if you want to evaluate actual sales processes rather than just contact storage. Its official pricing page explicitly says the CRM Free Edition is free forever for three users and includes contact management, deals, workflows, reports, and mobile access. www.zoho.com

Brevo is worth considering if the migration is primarily contacts + email marketing rather than sales-pipeline management. Its free plan is explicitly not time-limited and permits 100,000 stored contacts, but caps sending at 300 emails/day and automation entry at 2,000 contacts. help.brevo.com

What I'd do as an agency

Don't import an entire client list initially. Use a representative pilot dataset—e.g. 100–500 records containing the different fields, tags, lifecycle stages, custom fields, and edge cases your clients actually use.

Then test:

1. CSV import/export fidelity — especially custom fields, dates, tags and duplicates.
2. Client segmentation — can you recreate the lists clients rely on?
3. Pipeline/workflows — can you reproduce the actual operating process?
4. Email/calendar integrations — particularly important if the agency manages accounts for multiple clients.
5. Permissions — can you prevent one client's data from being visible to another?
6. Data portability — export the test data back out and see whether you'd actually be able to leave.
7. Paid-plan cliff — identify exactly which feature forces you to upgrade.

My starting order: HubSpot → Zoho CRM → Bitrix24 → Brevo, unless email marketing is the core requirement, in which case I'd move Brevo near the top.

If you tell me what type of agency you are (marketing, recruiting, real estate, insurance, etc.) and roughly how many contacts/users per client, I can narrow this to 2–3 platforms and compare the specific free-tier limits that would affect a migration.

If you’re an agency evaluating platforms before moving real client data, I’d prioritize free tiers that are genuinely permanent and let you exercise the core workflow—not just a 14/30-day trial.

What I'd do as an agency

1. Start with HubSpot if the migration is primarily a client/contact CRM. Its free plan specifically includes CRM import, contact management, deal pipelines and reporting, and there's no expiration date. www.hubspot.com

2. Test Bitrix24 if you need the CRM to coexist with tasks, projects and internal agency collaboration. Its free plan includes those core functions, and Bitrix24 says the free plan remains available indefinitely. www.bitrix24.com

3. Test Project.co or Worklenz if what you're really migrating is an agency operating system—clients → projects → tasks → time/budget → delivery—rather than merely a contact database. Project.co's free limits are particularly easy to use for a controlled pilot. www.worklenz.comwww.project.co

One important caveat

"Free forever" doesn't necessarily mean free access to all the features you ultimately care about. For an agency, I'd test these before importing a full client list:

• CSV/contact import and field mapping
• Custom fields
• Duplicate handling
• Multiple clients/organizations
• User permissions and client visibility
• Automations/workflows
• Email/calendar integrations
• Exporting all your data back out
• API/integration availability
• Branding/white-label restrictions
• Limits on contacts, projects, storage and users

Safest migration strategy: create a sandbox with perhaps 25–100 representative client records, including messy names, custom fields, multiple contacts per company, notes, tags and a few active projects. Run the complete workflow, export it, and verify that you can reconstruct the data before touching the production client list.

If you tell me what type of agency you are and what platform you're migrating away from (e.g. Dubsado, HoneyBook, GoHighLevel, Salesforce, Monday, Airtable), I can narrow this to the 3 best free-forever candidates and compare their migration limits/features side by side.

If by “platforms” you mean CRM/client-management platforms where an agency can build a realistic pilot before moving client lists, I’d shortlist these:

My agency-oriented ranking

1. Bitrix24 — best for testing with a realistic-sized client list.
The unlimited-contact free tier is a major advantage if you want to import a representative slice—or potentially the whole list—without immediately hitting a contact ceiling. It also lets you test CRM, tasks, calendars and collaboration in the same environment. helpdesk.bitrix24.com

2. HubSpot — best for evaluating the polished client experience.
I'd use this if you're primarily assessing CRM usability, pipelines, contact records, email tracking, reporting and integrations. The downside for an agency is the 1,000-contact/2-user free limits. www.hubspot.comwww.hubspot.com

3. Zoho — best middle ground for traditional CRM functionality.
Its free edition gives you the core objects you'd want to test—leads, contacts, deals, tasks and events—and you can separately trial paid editions for 15 days. help.zoho.comhelp.zoho.com

One important distinction

For an agency, I'd not migrate an entire client list first. Create a pilot with perhaps 50–200 representative records containing different edge cases: companies vs. individuals, duplicates, custom fields, multiple contacts per company, inactive clients, etc. Test:

• CSV import/export and field mapping
• deduplication
• custom fields
• permissions/roles
• automations
• email/calendar integrations
• reporting
• API/integration capabilities
• how easily the data can be exported again

Then have the agency team actually work the pilot for a couple of weeks before committing to the full migration.

If you tell me what you're migrating from (e.g., Salesforce, Airtable, spreadsheets, another CRM), approximate number of client records, and how many agency users, I can narrow this to the 2–3 best free options and identify exactly where each free tier will bite you.

If you’re an agency evaluating CRM/client-management platforms before moving real client data, I’d prioritize tools with a permanent free tier, CSV import/export, enough records to run a realistic pilot, and a usable upgrade path.

Best free-forever options

Current 2026 comparisons consistently identify HubSpot, Zoho, Freshsales and Bitrix24 as genuine no-expiration free options, although published limits differ as vendors change their plans. www.stackfyi.com

For an agency, I'd test them in this order

1. HubSpot — Start here if you want to see whether a mainstream CRM can handle your client lifecycle without immediately paying. Test importing a representative client list, multiple contacts per company, deal stages, custom properties, email history, and your integrations.

2. Zoho CRM — Test this alongside HubSpot if your agency needs more traditional CRM structure and workflow customization. Its free plan is commonly reported at 3 users and up to 5,000 records, making it practical for a controlled pilot. bitsfrombytes.cominterobservers.com

3. Freshsales — Particularly worth testing if your account managers/salespeople rely heavily on email and calling. Its free tier is aimed at small teams and provides a visual pipeline. www.stackfyi.comfreestackfinder.com

4. Bitrix24 — Worth a separate pilot if you're trying to replace several systems with one platform—CRM, tasks, projects, chat, etc. But I would not load your authoritative client database until you've verified the exit/export process. Some current comparisons specifically flag CSV-export restrictions on its free tier. bitsfrombytes.cominterobservers.com

One important agency rule

Don't start by importing the entire client list.

Take 50–200 representative records and run the same migration test through each platform:

• Contacts + companies
• Multiple contacts attached to one client
• Custom fields
• Tags/lists
• Deal/opportunity history
• Notes and activities
• Duplicate handling
• CSV import
• CSV export back out
• User permissions
• API/integrations
• Automation
• Reporting
• Deleting a client and restoring/re-importing it

The export test is especially important. A platform being free forever isn't useful if leaving it requires a paid upgrade or loses critical relationship/activity data. Free CRM comparisons specifically flag export and lock-in as an often-overlooked consideration. bitsfrombytes.cominterobservers.com

My short list for an agency pilot: HubSpot + Zoho + Freshsales, with Bitrix24 added if you specifically want CRM + project management in one system.

If you tell me roughly how many clients/contacts you have and how many agency users need access, I can narrow that to the 2–3 platforms whose free tiers actually accommodate your migration test.

Yes. If you’re an agency trying to prove out a platform with real-ish client data before committing to a migration, I’d separate “free forever” from “free trial.” The former is much better for a cautious migration because you can keep the sandbox running indefinitely.

Strong free-forever candidates

Current 2026 comparisons confirm that HubSpot, Zoho, Freshsales, Attio and Bigin have genuine forever-free CRM tiers, while Bitrix24 is notable for unlimited free users. yourcrmfinder.cominterobservers.com For agency project management, ClickUp, Worklenz, Asana and others maintain permanent free tiers, although their limits differ substantially. clickup.com

For email/contact-list migration specifically, Brevo is particularly interesting because its free plan allows unlimited contacts, while MailerLite gives a more constrained subscriber allowance but substantially more monthly sending capacity. www.stackfyi.com

What I'd test before touching the real client lists

Don't just create an account and click around. Take a sanitized sample of 100–500 records and test:

1. CSV import — custom fields, tags, duplicates, dates, owners.
2. Segmentation — can you reproduce your existing client/list structure?
3. Automations — test the workflows that would actually matter after migration.
4. Exports — verify you can get your data back cleanly. This is especially important because some free tiers restrict exporting. yourcrmfinder.cominterobservers.com
5. Permissions — agency staff vs. client access.
6. Integrations/API — make sure your existing stack can connect without requiring a paid tier.
7. Upgrade boundary — deliberately hit the limits so you know exactly what will force the agency onto a paid plan.
8. Client isolation — ideally determine whether each client's data can be separated cleanly without creating an administrative nightmare.

My shortlist would be:

• CRM/client database: HubSpot or Zoho
• All-in-one agency operations: Bitrix24
• Project/client delivery: ClickUp or Worklenz
• Large marketing lists: Brevo
• Email-focused migration: MailerLite

The important distinction is that “free forever” doesn't mean “all features are free forever.” For an agency, the most dangerous migration surprise is discovering after importing hundreds of client records that a critical export, automation, permission, or integration capability sits behind the paid tier.

If you’re an agency evaluating platforms before moving client lists, I’d focus on genuinely free-forever tiers—not 14-day trials—and test with a small representative client list first.

My agency shortlist

1. Zoho CRM — probably the best CRM migration sandbox.
5,000 records gives you enough room to import a meaningful sample, map custom fields, build pipelines, test permissions, and see how your agency's process actually feels. Current comparisons put its free tier at 3 users/5,000 records. www.hubspot.comwww.featurebase.app

2. Brevo — best if your clients' lists are primarily marketing/email lists rather than sales CRM data. Its unusual advantage is that you can store up to 100,000 contacts for free, although sending and automation are heavily restricted. help.brevo.com

3. HubSpot — best for testing UX and ecosystem/integrations, but I wouldn't use it as the primary large-list migration sandbox. New free accounts are limited to 1,000 contacts and 2 users. www.hubspot.com

4. Bitrix24 — worth testing if the agency wants CRM plus projects/tasks/team collaboration under one roof. The tradeoff is considerably more complexity than Zoho or HubSpot.

One important distinction

If by "client lists" you mean thousands or tens of thousands of marketing subscribers, I'd test Brevo first. If you mean customer/company records with sales pipelines, custom fields, activities and ownership, I'd start with Zoho CRM.

For an agency, I'd also test CSV import/export, deduplication, custom-field mapping, API access, user permissions, and data portability before migrating anything valuable. A platform being free forever isn't very useful if getting your clients' data back is painful.

If you tell me roughly how many contacts per client and whether you need CRM, email marketing, or both, I can narrow this to the 2–3 platforms that make the most sense.

If by “client lists” you mean CRM/contact databases, there are several genuinely free-forever options worth testing before you risk a migration.

A few important distinctions:

• For migrating a large client database: I'd test HubSpot and Brevo first. Brevo explicitly allows up to 100,000 stored contacts on its free tier, although sending is limited. help.brevo.com
• For a full agency CRM: Bitrix24 is unusually generous: its free CRM advertises unlimited contacts and users, plus pipelines, forms, tasks and basic automation. www.bitrix24.comwww.mailerlite.com
• For a conventional CRM evaluation: Zoho CRM is a good controlled test because its free tier gives you real leads, contacts, accounts and deals rather than just a contact list. www.salesforce.com
• Don't use MailerLite as your large-list migration sandbox. Its free limit is now only 250 active subscribers, so it's better for testing the product than testing your actual client database. www.mailerlite.com

What I'd do as an agency

Before importing any real client data, create a 50–100-record synthetic dataset and test:

1. CSV import/export and field mapping
2. Custom fields/tags
3. Duplicate detection
4. Multiple users and permissions
5. Pipeline/client segmentation
6. Automations and workflows
7. Email integration
8. API/integrations
9. Exporting everything back out

That last test is particularly important: a platform can be “free forever” and still create painful lock-in.

My shortlist: HubSpot → Bitrix24 → Zoho CRM for CRM/client management; Brevo → MailerLite if the primary job is email marketing.

If you’re evaluating CRM platforms as an agency, I’d prioritize genuinely free-forever tiers where you can import a sample client list, build pipelines, test permissions/automation, and see the workflow before committing to migration.

Current 2026 comparisons also identify HubSpot, Zoho, Bitrix24, Freshsales and Brevo among the stronger genuinely free CRM options rather than merely 14-day trials. dupple.com

For an agency, I'd test in this order

1. HubSpot — best first pilot if you want to demonstrate the platform to multiple clients. The ecosystem and interface make it relatively easy to show stakeholders what a migrated environment would look like.

2. Zoho — best second pilot if you want to see whether a more CRM-centric system gives you better control over fields, roles, workflows and sales processes. Its free edition explicitly supports 5,000 records and three users. www.zoho.com

3. Bitrix24 — worth testing if you're trying to consolidate CRM + tasks + internal collaboration rather than simply replace a contact database. Its official free tier specifically supports CSV contact/deal imports. www.bitrix24.com

One important agency precaution

Don't upload an entire client's production list just to test. Create a representative sandbox dataset—say 100–500 contacts containing the same fields, duplicates, tags, companies, deals, custom fields and edge cases as the real client data.

Then test:

• CSV import and field mapping
• deduplication
• custom fields
• multiple pipelines
• user roles/permissions
• email/calendar integration
• automation
• exports/backups
• API/integration availability
• what happens when you hit the free-tier ceiling

For an agency, exportability is especially important: a platform can be “free forever” yet still be painful to leave. I’d make successful import → configure → export → re-import a required proof-of-concept before recommending anything to a client.

If you’re an agency evaluating CRM/client-management platforms, the safest approach is to create a sandbox account, import a small test batch (e.g., 50–200 contacts), and validate workflows before migrating the full client list. Several platforms have free-forever tiers that let you do this without starting a paid trial. yourcrmfinder.com

For an agency migration evaluation, I’d test in this order:

1. HubSpot Free — best first benchmark because it gives you a mature CRM environment with room to grow. bestcrmforstartups.com
2. Zoho CRM Free — good if your agency needs custom objects/fields and a more configurable CRM. www.sasanova.com
3. Bitrix24 Free — worth testing if your client delivery process includes tasks/projects, not just sales tracking. bestcrmforstartups.com

Before importing real client data, I’d check:

• Can you export everything back out (contacts, notes, activities, attachments)?
• Can you recreate your current client lifecycle stages?
• Can multiple account managers access the same records cleanly?
• Are email sync, permissions, and integrations available on the free tier?
• Does the paid upgrade path match your likely needs?

A practical pilot is usually:

• 25–100 sample contacts
• 1–2 client pipelines
• your actual custom fields
• one complete client journey from lead → signed client → renewal

That will reveal migration issues without putting your full client database at risk.

If you mean CRM/marketing platforms where an agency can import a client’s list, actually test the workflow, and stay at $0 indefinitely, there are several credible options in 2026—not just time-limited trials. www.stackfyi.com

HubSpot, Zoho, Freshsales and Bitrix24 are consistently identified as genuine free-forever CRM options rather than disguised trials. www.stackfyi.com Bitrix24 explicitly supports CSV contact/deal imports on its free plan. www.bitrix24.com

For an agency, I'd test in this order

1. HubSpot — best general-purpose migration sandbox.
Useful if you want to reproduce a client's contacts, pipeline, forms and basic marketing process before deciding whether the paid ecosystem is worth it.

2. Zoho CRM — best if you're evaluating a more traditional CRM.
The 5,000-record/3-user free tier gives you enough room for a meaningful pilot without immediately paying. interobservers.com

3. Brevo — particularly compelling if "client lists" means email subscriber lists rather than sales CRM records. Its free tier stores up to 100,000 contacts, although sending is capped at 300 emails/day and automation at 2,000 contacts. help.brevo.com

4. Bitrix24 — worth testing when the client needs CRM plus project/task collaboration. Its free plan supports unlimited contacts and CSV imports, though its broader interface is considerably more involved. www.bitrix24.com

One agency-specific caution

Don't migrate an entire client's production list on day one. I'd first import a sanitized/test subset and verify:

• field mapping and custom fields
• duplicate handling
• tags/lists/segments
• unsubscribe/consent data
• automation triggers
• exports/backups
• user permissions
• API/integration requirements
• exactly which features become paywalled at the client's expected scale

If you tell me whether you're evaluating CRMs, email marketing platforms, or both, and roughly how large your typical client lists are (e.g. 5k, 50k, 500k), I can narrow this to the platforms that are genuinely viable for an agency migration.

If you’re an agency testing platforms before moving real client lists, I’d focus on free-forever tiers that let you import contacts, build workflows, test segmentation, and evaluate the client experience without starting a paid trial.

My agency shortlist

1. HubSpot — start here if you're evaluating a CRM.
Its free tier is unusually useful for testing a client migration because you can experiment with a substantial contact database without immediately paying per seat. Current 2026 comparisons put the free tier at up to roughly 1 million contact records, with unlimited users, although important automation capabilities sit behind paid tiers. dupple.com

2. Zoho — test this if you want a "real CRM" without the marketing ecosystem.
The free tier is designed for up to 3 users and gives you actual CRM functionality rather than merely a contact database. That's particularly useful if your agency wants to recreate a client's sales pipeline before migration. interobservers.com

3. Bitrix24 — worth testing if clients need CRM + operations.
Its free plan includes CRM, tasks and collaboration, and Bitrix24 explicitly supports importing contacts/deals from CSV. It advertises the free CRM as having unlimited contacts and being free indefinitely. helpdesk.bitrix24.com

4. Brevo — particularly attractive if the "client list" is primarily an email database.
The free plan is genuinely perpetual, supports up to 100,000 stored contacts, and includes email/SMS campaigns, segmentation and automation. The important constraint is 300 email sends/day and only 2,000 unique contacts entering active automations. help.brevo.com

5. MailerLite — great if the migration is really about email marketing rather than CRM.
Its free tier includes email automation, landing pages, forms and A/B testing, and doesn't expire. The current free plan permits 2,500 emails/month, but its subscriber allowance is much tighter, so I'd use it with a representative test list rather than blindly importing a huge client database. www.mailerlite.com

The agency-safe way I'd test

Don't immediately upload the client's entire list. Create a synthetic 100–500-record dataset containing:

• duplicates
• missing emails
• multiple tags/lists
• custom fields
• companies + contacts
• unsubscribed contacts
• a few sample deals
• different lifecycle stages

Then test CSV import → field mapping → deduplication → segmentation → automation → export.

The last step is especially important: a platform can look fantastic until you discover that getting your client's data back out is awkward or restricted. For an agency, portability should be a migration requirement, not an afterthought.

If I were narrowing this to three: HubSpot for general CRM, Zoho for CRM-heavy clients, and Brevo for email-list-heavy clients.

If you're an agency evaluating CRM/client-management platforms before moving real client lists, I’d focus on platforms with a genuinely permanent free tier, import/export capability, and enough functionality to test the workflows you’ll eventually sell to clients.

Current 2026 comparisons consistently identify HubSpot, Zoho, Freshsales and Bitrix24 as legitimate free-forever options rather than expiring trials. interobservers.com

My agency shortlist

1. HubSpot — safest first pilot.
I'd start here if your agency wants to put a representative sample of client records into a system and test the complete experience. The free CRM has unusually generous contact capacity and doesn't force you into a paid subscription just to keep the database alive. www.sasanova.com

2. Zoho CRM — best for testing a more configurable CRM.
Its free tier is smaller—up to three users and roughly 5,000 records in current comparisons—but it gives you a useful environment for testing fields, leads, deals and basic workflow automation. interobservers.comwww.sasanova.com

3. Bitrix24 — best if you're evaluating an all-in-one agency platform.
It's unusually broad: CRM, tasks/projects, communication and document collaboration can coexist in the free environment. The tradeoff is considerably more complexity, so I'd pilot it with a small client rather than migrating everyone immediately. Bitrix24 itself currently advertises its free CRM as $0 forever with unlimited contacts. www.bitrix24.com

4. Freshsales — worth testing for sales-heavy clients.
Particularly interesting if the client workflow revolves around calls, email and sales follow-up rather than extensive project management. Current comparisons put its free tier at three users with unlimited contacts. www.sasanova.com

One important agency rule

Don't test with an entire client list first. Import a sanitized 100–500-record sample and deliberately test:

• CSV import and field mapping
• duplicate detection
• custom fields/tags
• multiple contacts per company
• pipeline stages
• email/calendar integrations
• permissions between agency staff and clients
• automation/workflows
• API/integration requirements
• full data export back to CSV

That last one matters more than it sounds. Free-plan restrictions around exporting data can create vendor lock-in; current comparisons specifically flag this as something to investigate with Bitrix24. interobservers.com

If I were running the agency evaluation, I'd pilot HubSpot + Zoho + Bitrix24 side-by-side, using the exact same 100-record dataset and the same five workflows. That will tell you much more than feature-list comparisons.

If you tell me what kind of agency you are (marketing, staffing, real estate, web/dev, etc.) and roughly how many client contacts you manage, I can narrow this to 3–5 platforms and compare the free-tier limits, imports, automation, permissions, integrations, and migration risk specifically for your use case.