Sending

Email suppressions

The account-wide suppression list: how recipients are added and how suppressed sends are skipped.

MailBlastr maintains an account-wide suppression list of addresses you should no longer email. Any send — single, batch, scheduled, or campaign — skips recipients on this list before queuing the message for delivery.

How addresses are added

A recipient is added to your suppression list when:

They hard-bounce — a permanent bounce. See Email bounces.
They complain — they mark a message as spam (a complaint).
They unsubscribe — via a campaign unsubscribe link, or a manual unsubscribe you record.

Not every mailbox provider reports a complaint — most notably Gmail / Google Workspace does not emit a complaint when a recipient marks a message as spam. So a missing complained event does not mean a message was well received.

How suppression is applied

Before each send, MailBlastr checks every recipient (across to, cc, and bcc) against your suppression list and removes any matches. Matching is case-insensitive.

If *some* to recipients are suppressed, they are dropped and the email is sent to the remaining recipients.
If all to recipients are suppressed, the send is rejected with a validation_error — there is no one left to deliver to.

Suppression is scoped to your account: an address you suppressed never affects another account, and another account's suppressions never affect yours.

Suppression is a deliverability and compliance safeguard. Mailing recipients who bounced, complained, or unsubscribed harms your reputation and can violate anti-spam regulations — the list is enforced on every send path for this reason.

If you remove an address from the suppression list and it bounces or is marked as spam again, it will simply be suppressed again. Repeatedly mailing addresses that bounce or complain negatively impacts your sender reputation.