A suppression list is a memory of who not to email. Once an address has hard bounced or complained, the list makes sure you never send to it again, whatever your own database says.
Why it exists
The same address, mailed again and again, is the cheapest way to wreck your rates. A mailbox that does not exist will bounce every time, and a person who complained once will complain again. Both land on the numbers AWS reviews: the bounce rate and the complaint rate.
Suppression lists in Amazon SES
SES has two.
- The account-level suppression list belongs to your account. Accounts that started using SES after 25 November 2019 use it by default for both bounces and complaints; older accounts have to enable it. Each entry records the reason,
BOUNCEorCOMPLAINT, and you can add or remove addresses yourself through the console or the API. - The global suppression list is run by AWS. When you use your account-level list, SES also adds addresses that cause hard bounces to the global list. You cannot edit it, and an address that is only on the global list can still be attempted, so if it bounces it counts toward your rate.
When you send to an address on your account-level list, SES accepts the message but does not send it. It reports a bounce with the subtype OnAccountSuppressionList, and that does not count toward your bounce rate. It does count toward your daily sending quota.
The problem with the SES list
It is an API and a console table. Searching it, filtering by reason, expiring an entry after a few days or exporting it for another system is something you script yourself. That gap is where most teams end up with a spreadsheet.
Good habits
Keep your own sending code in sync with the list, so your application stops queuing mail to addresses SES will refuse. Treat complaint entries as permanent. Review bounce entries when you have fixed the cause, not before.
Common questions
Should I ever remove an address from the suppression list?
Rarely. Do it when you know the cause is fixed, for example a mailbox that was full and is now cleared, or an address that was added by mistake. Removing a complaint is almost never a good idea.
What is the difference between the account list and the global list?
The account-level list is yours: you can read it, add to it and remove from it. The global list is managed by AWS and covers addresses that have bounced across Amazon SES, so you cannot edit it.
Does a suppressed address count toward my bounce rate?
Not if it is on your account-level list. SES does not count those messages toward your bounce or complaint rate, although they do count toward your daily sending quota.