Suppression list
A suppression list is the set of addresses you must not send to: hard bounces, spam complaints, and anyone who has unsubscribed. Checking it before every send is what stops a dead address being retried until it costs you your reputation. The list is also evidence, because it is the record that an unsubscribe was honored.
At a glance
- Category
- Deliverability
- Contains
- Hard bounces, complaints and unsubscribes
- Written
- Automatically, at the moment the signal arrives
- Checked
- Before every send, transactional and bulk alike
- Scope
- Per account, across every domain and every key
- Editable
- Over the API, for the rare case that needs it
How it works
Three kinds of signal write to the list: a permanent bounce, a complaint, and an unsubscribe. Each is recorded with its reason and the time, and the list is consulted before any message is queued. A suppressed address is skipped rather than attempted, so nothing is sent and nothing is charged. Because the list is held at the account level rather than per campaign, an address suppressed by one system cannot be reached by another that has not heard about it.
Why it matters
Suppression is where several separate obligations are met at once, which is why it works best as infrastructure rather than as a step somebody remembers. It protects reputation by not retrying dead addresses, it protects the reader by honouring their departure everywhere, and it protects you by keeping a dated record that the departure was honoured. A team without one ends up with the same address on three lists and one of them still mailing it.
Example
A message to a former employee is refused permanently, and the address is suppressed with the reply the server gave. A week later a different service in the same company tries to mail that address as part of a campaign; the send is skipped before anything leaves. A year after that, somebody asks whether the address was ever contacted again, and the list answers the question with a date and a reason.
Common mistakes
- 01Keeping the list per campaign or per tool, so an unsubscribe in one place has no effect in another.
- 02Suppressing on temporary bounces, which removes real customers whose mailbox happened to be full for an afternoon.
- 03Removing an address from the list because a colleague insists it is valid, which usually recreates the bounce that put it there.
- 04Treating suppression as applying only to marketing, when a permanently bounced address cannot receive a receipt either.
In Rasket
Suppressions are per team, written automatically on permanent bounces and complaints, checked before every send, and editable over the API. Suppressions reference
Related terms
Frequently asked questions
Does suppression apply to transactional mail too?
A hard bounce does, because the address simply does not work. An unsubscribe applies to marketing only, so a password reset still goes out to somebody who left a newsletter.
Can I remove an address from the suppression list?
Yes, over the API, and it is occasionally the right thing to do when somebody signs up again from a previously bounced address. Removing entries because the list looks large is how reputation problems start.
Is the list per domain or per account?
Per account, which is the point. An address that complained about one of your domains should not be reachable from another one belonging to the same sender.
Last updated 16 September 2026.
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