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Suppressions

A suppression is an address your project must not mail again: it hard bounced, or the recipient marked your mail as spam. Sending to these addresses anyway damages your sender reputation, so Mailway blocks it at the source.

How addresses get suppressed

Section titled “How addresses get suppressed”
  • Automatically — when a provider reports a hard bounce or a spam complaint through delivery events (Amazon SES, SendGrid, Mailgun, Postmark, Mailtrap, Mandrill, Brevo, Resend, Mailjet, MailerSend, Nuntly, SMTP2GO; every supported provider except Gmail / Google Workspace and generic SMTP), the recipient lands on the project’s suppression list with the reason attached.
  • Manually — add an address in the console (Suppressions page), e.g. for a recipient who asked you directly to stop (Pro and up).

Suppressions are per project: a bounce on your marketing project doesn’t block a password reset from your transactional project.

Per project also means not per provider — and that’s the point. A hard bounce reported by Amazon SES suppresses the address for every provider attached to the project: the same address won’t go out through SendGrid or Mailgun tomorrow either. Each provider alone only ever learns from its own traffic; because all of yours report back into one gateway, what one provider learns protects your sends through all of them.

What happens on send

Section titled “What happens on send”

Both send paths check the list:

  • The HTTP API rejects up front — 422 with code suppressed_recipient, naming the blocked addresses — so your app knows immediately.
  • Mail entering through the SMTP relay is received (SMTP has no way to reject one recipient of many cleanly), then stopped before any provider handoff and marked accordingly in the console. A mail.suppressed webhook event fires.

On the SMTP path the stopped mail shows as Rejected (API value failed) with the blocked address named — troubleshooting if you’re tracking down why a send didn’t go out.

Un-suppressing

Section titled “Un-suppressing”

Addresses can be removed in the console by admins and developers on that project, and every change is recorded in the team’s security history (shown on the Audit log page, Business and up). Un-suppress deliberately: if the address hard-bounced yesterday, it will hard-bounce today, and repeat bounces are exactly what mailbox providers punish.

Matching is case-insensitive on the full address.