What is the suppression list for?

Think of it as a do-not-email list. Every account has one and subscribers are typically added to the list because they have been unsubscribed, or emails sent to the email address have bounced.

With these inactive subscribers recorded in your account as "suppressed" it prevents any further emails being sent to them. This keeps list sizes in check and helps to protect your sender reputation.

On this page:

How subscribers are added to the suppression list

There are rules in place in your account to add subscribers to the list automatically, but you can also add people manually.


Any subscriber who meets the following criteria is added to the suppression list automatically:

  • They unsubscribe themselves using a form or unsubscribe link in an email. Or, their status is changed to unsubscribed through your account.
  • The subscriber marks one of your emails as spam.
  • An email sent to the subscriber results in a hard bounce.
  • The last five campaigns sent to the subscriber soft bounced, resulting in the email address being converted to a hard bounce status.

Learn more about how the bounce rules work for hard and soft bounces.


Adding email addresses manually is good practice to ensure that people marked "do not email" in an external system – for example, a CRM tool – are not imported to a list accidentally.

For instructions on adding, and removing, subscribers from your suppression list, see our page on suppression list management and settings.

How the suppression list works

Whenever you import subscribers to a list in your account, we scrub it against the suppression list to check for a match. If any matches are found, those email addresses will not be imported. An import report will display on screen showing the number of subscribers not added because they are "Suppressed," as shown here:

Important suppression list details:
  • If an email address is on your suppression list, it does not prevent someone from resubscribing with the same email address if they sign up "organically" through a subscribe form.
  • The suppression list only stops matching addresses from being imported to a list. If someone changes a subscriber's status from "Bounced" or "Unsubscribed" back to "Active," they will be sent any emails you send to that list, even though they remain on the suppression list.
  • The suppression list will not prevent email addresses being re-added via an API call.

Accessing your suppression list

Open Lists & Subscribers, then below the lists, or list, click suppressed to open the "Manage your suppression list" page:

Here you can see the date each email address was added, and the reason. The most common reasons are "Unsubscribed" or "Bounced." If the reason is "Suppressed" it means the email address was added manually. If it says "Reason unavailable" the email was added some time ago, before reasons were recorded.