The suppression list

The suppression list is the set of addresses that will never be sent to, no matter which audience they appear in. Open Suppressions to see it.

Each entry shows the Email, the Reason it was suppressed and when it was Added. You can search the list by email.

It mostly fills itself

Bounces and complaints are added automatically as they happen — the page says so: "Bounces and complaints from SES will appear here automatically." Unsubscribes are captured the same way.

This is why you do not need to prune lists by hand, and why a campaign's recipient count is usually lower than its audience size.

Adding one yourself

Use Manually suppress an email to add an address directly. Enter the email and a reason.

Worth doing when someone asks to be removed by replying to you or contacting support, rather than clicking unsubscribe — suppressing them yourself honours the request everywhere at once, instead of relying on remembering to skip them.

Suppression versus deletion

Suppressing is not deleting. The contact stays in your audiences and reporting; they simply stop receiving mail. That is usually what you want — deleting a contact loses the record that they asked not to be emailed, and a later import could quietly re-add them.

Why an address will not come off

Suppressions exist to protect your ability to reach the inbox. An address that hard-bounced does not exist, and an address that filed a complaint asked not to hear from you. Removing either from the list to email them again is the fastest way to a deliverability problem.

Next: open Suppressions and search for the address you are asking about — the Reason column explains why it stopped receiving mail.