Integrations overview: how the 17 ESP/CRM connections work

Valid Email Checker connects natively to 17 email service providers (ESPs) and CRMs. Once connected, you can verify lists from those platforms without exporting CSVs and re-uploading — the entire flow runs through the dashboard. This guide covers everything common across the 17 integrations: the connect flow, how list selection works, the two cleanup modes, default settings, and the platform-specific quirks to know about.

For platform-specific walkthroughs, see the per-platform guides linked at the bottom.

The 17 supported platforms

How the connect flow works

The same UI handles all 17 platforms. Some use OAuth (one-click redirect to authorize) and the rest use API-key authentication (paste a key generated from your platform dashboard).

Step-by-step

1. Open Bulk Upload in the dashboard sidebar.
2. Click Connect Email Platform (or go to Integrations → Add Connection from the sidebar).
3. Pick your platform from the grid. The auth method shows on the card — OAuth platforms have a "Connect with [platform]" button; API-key platforms show a key input field.
4. For OAuth: click Connect → land on the platform's auth page → approve the requested read/write permissions → redirect back to our dashboard with the connection ready.
5. For API key: paste the key into our form. Some platforms also need additional fields (account region, region-specific subdomain) — those appear when relevant.
6. Optionally give the connection a name. Useful for managing multiple accounts of the same platform.
7. Click Save Connection. Your lists from that platform sync automatically.

Where to find API keys

Each platform exposes API keys somewhere different in their dashboard. The per-platform guides walk through exactly where for each platform. A general pattern: look for Settings → API, Integrations, Developer, or Account → API Keys.

Picking a list to verify

After connecting, you see a picker showing every list/audience/segment available in the connected account. The specifics vary by platform:

• Mailchimp — Audiences and segments.
• HubSpot — All Contacts, Static lists, Active lists.
• Klaviyo — Lists and segments.
• Most others — Lists (static), sometimes also segments or tags.

Each list shows the subscriber count so you know exactly how many credits the verification will consume (1 credit per address, with auto-refunds for unknown results).

The two verification modes

Verify Only (default)

We pull the list from the platform, verify every address, return detailed results in your Valid Email Checker dashboard. Your data in the source platform is completely unchanged. You decide what to do with the results — export, segment, or manually clean.

When to use it:

• You want to evaluate list quality before committing to any cleanup action.
• You want to manually review borderline cases (catch-all results, role accounts) before deleting anything.
• Your platform requires manual list management for compliance reasons.
• You want to use the results to inform segmentation rather than clean up the source list.

Clean list automatically

We verify the list and apply cleanup actions back to the platform based on rules you configure. Five result categories appear in the settings panel. Each has an Enable toggle and an Action selector (Keep, Unsubscribe, Delete).

The three action types

• Keep — leaves the contact untouched in the source platform. Their record stays exactly as it was before verification.
• Unsubscribe — marks the contact as unsubscribed in the source platform. They stay in your account but stop receiving marketing email.
• Delete — removes the contact from the source platform entirely. Permanent on most platforms; some keep audit metadata.

Multiple connections of the same platform

Most integrations support connecting more than one account of the same platform. Useful for agencies managing several clients on the same ESP, businesses with separate HubSpot portals per region or product line, or teams that want production and staging connections.

1. Connect the first account through the standard flow.
2. Go to Integrations → Add Another Account for the same platform.
3. Repeat the connect flow with the second account's credentials.
4. Give each connection a clear name — client name, business unit, region, or environment.

When verifying, you pick which connection to use. The list picker shows lists from only that one connection so you do not have to disambiguate across accounts.

Refreshing list data

Lists sync automatically when you connect a platform. If you have added new contacts to the source platform, created new lists, or want to see updated subscriber counts before kicking off a verification, click Sync Now on the relevant connection — that pulls fresh data from the platform API without you having to reconnect.

Cost

1 credit per address verified. Same rate as a bulk upload, same rate as an API call. The integration itself is free — there are no per-integration fees or seat charges. You control spend by picking the right list (e.g., a HubSpot active list filtered to "created in the last 30 days" verifies just the newcomers — cheap monthly hygiene).

Credit refunds apply the same way they do elsewhere: unknown results auto-refund, unprocessed bulk rows auto-refund, duplicates are stripped before charging.

What we read vs. what we write

Across every integration:

• We read lists/audiences/segments and their members so we can verify the addresses.
• In Clean List Automatically mode, we write only the cleanup actions you configured back to the source platform.
• We only touch the email field. Other contact properties — names, company, phone, custom fields — are never modified.
• Contact activity history is preserved regardless of cleanup actions.
• We never send email through your platform or count against your sending limits.

Common gotchas across platforms

Auth method confusion

Some platforms call their API key by a different name — "Access Token", "Personal Token", "Private API Key". Look for whatever the platform offers under Settings → API. If you cannot find it, the per-platform guides have explicit instructions per platform.

Permission requirements

OAuth platforms (HubSpot, Mailchimp) require account admin or super-admin permissions to authorize third-party apps. If the connection fails at the authorization step, you likely need a higher role inside the source platform — ask your account admin to authorize.

API key scope

Some platforms let you generate scoped API keys (read-only, write-only, full-access). Make sure the key you generate has at minimum read access to contacts/lists and write access for unsubscribe/delete if you want Clean List Automatically mode. Read-only keys work for Verify Only mode but reject any cleanup write.

Webhook/callback delays

After Clean List Automatically completes on our end, the source platform may take a few seconds to a few minutes to reflect the changes. If you check Mailchimp immediately after verification and the contacts are still showing as subscribed, give it 2-3 minutes — the cleanup writes are queued and processed asynchronously on most platforms.

When to use bulk upload instead

Even if your platform is on our integrations list, you might still prefer bulk upload sometimes:

• You want to verify a list you exported six months ago (the integration always pulls current data).
• You want to verify contacts across multiple platforms in a single job (export each, merge, upload).
• You want to verify a list before importing it into a platform (verify clean → import).
• Your source platform is not on the integrations list at all.

See the bulk verification complete guide for that path. The verification engine and credit cost are identical regardless of which path you take.

Common questions

Does Valid Email Checker send any email through my platform?

No. We never send email through your ESP/CRM. Verification is server-to-server SMTP handshakes with the recipient mail providers — not through your platform. Your sending limits and your contacts are unaffected.

Will my contacts know they were verified?

No. Verification is passive. Your contacts never see any email or notification from us. The only visible change is whatever cleanup action you configured being reflected in your source platform afterward (and that looks like normal list management, not an external action).

What if my platform is not on the integrations list?

Two options:

• Bulk upload — export a CSV from your platform, upload to us, download the cleaned file, re-import. Tedious for daily use, fine for occasional cleanups.
• REST API — wire verification directly into your platform via our API (which unlocks after your first credit purchase). Gives complete flexibility for any platform with an API of its own.

If you want a native integration with a platform we do not support, email support@validemailchecker.com. We prioritize new integrations based on customer demand.

Can team members connect their own integrations?

Yes. Team members can connect and use their own integrations, run verification jobs through them, and view results. They cannot purchase credits or access API keys, but the integration surface is fully available to them. See team member guide.

What happens to my connections if I cancel my subscription?

Your connections stay configured but go inactive once the subscription expires and Monthly credits zero out. Any PAYG credits in your account still work, so you can keep verifying through the integrations — just at PAYG rates and against your PAYG balance. Connections themselves do not expire.

Per-platform guides