What is a suppression list?
A suppression list is a list of email addresses that should never receive emails from you. When you attempt to send an email to a suppressed address, the email service blocks the send before it leaves the server. Suppression lists exist to protect your sender reputation and to respect recipients who don’t want your emails.Why suppression lists exist
Sending emails to addresses that have previously bounced, complained, or unsubscribed causes real damage:
Email providers track all of these signals. Repeatedly sending to suppressed addresses tells them you’re either not maintaining your list or intentionally ignoring negative signals — both of which destroy trust.
How suppression works in SendKit
SendKit maintains a suppression list for each team. Addresses are added automatically when:
When you try to send to a suppressed address, SendKit blocks the send and returns an error:
Types of suppression
Bounce suppression
When an email hard bounces (address doesn’t exist, domain doesn’t exist), the address is automatically suppressed. This prevents you from repeatedly hitting invalid addresses and driving up your bounce rate.Complaint suppression
When a recipient marks your email as spam, the address is automatically suppressed. This prevents you from sending more emails to someone who clearly doesn’t want them — which would generate more complaints.Manual suppression
You can manually add addresses to your suppression list. Use this when:- A recipient asks to be removed outside of the normal unsubscribe flow
- You know an address is invalid or problematic
- You’re cleaning your list proactively
Managing your suppression list
You can view and manage your suppression list from the SendKit dashboard or via the API:- View suppressed addresses — see all suppressed addresses and the reason they were suppressed
- Add addresses — manually suppress an address
- Remove addresses — unsuppress an address (use with caution)
Removing an address from the suppression list
You can remove a suppressed address, but do so carefully:- Bounced addresses — only remove if you’ve confirmed the address is now valid (e.g., the recipient reached out to say their mailbox was fixed)
- Complained addresses — only remove if the recipient explicitly asks to receive your emails again
- Manually added — remove when the reason for suppression no longer applies
Suppression list vs unsubscribe list
These are related but distinct:
A suppressed address receives nothing. An unsubscribed address receives no marketing emails but still gets transactional emails (password resets, receipts, etc.).
Best practices
Never circumvent the suppression list
If you export your contacts and re-import them, the suppression list still applies. SendKit checks every send against the suppression list regardless of how the recipient was added.Don’t remove bounced addresses without verification
“Maybe the address works now” is not a valid reason to unsuppress. Verify first — ideally by having the recipient contact you directly.Import existing suppressions
If you’re migrating from another email service, import your existing suppression list into SendKit. This prevents you from sending to addresses that already bounced or complained on your previous service.Monitor suppression growth
A rapidly growing suppression list can indicate problems:- Many bounces — your list has hygiene issues
- Many complaints — your content or targeting needs improvement
- Both — stop and reassess your email strategy
FAQ
Does the suppression list apply to transactional emails too?
Does the suppression list apply to transactional emails too?
Yes. A suppressed address is blocked from receiving any email — transactional or marketing. If a user needs to receive transactional emails (like password resets) but was suppressed due to a complaint, you’ll need to remove them from the suppression list.
What happens if I send a batch that includes suppressed addresses?
What happens if I send a batch that includes suppressed addresses?
SendKit skips suppressed addresses in the batch and delivers to the rest. The suppressed sends are not counted against your quota. You won’t receive an error for the batch as a whole — individual suppressed addresses are silently skipped.