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 helps to prevent 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:


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

When you import subscribers — by adding their details manually or by importing a list — we check the imported email addresses against email addresses on the suppression list. If any matches are found, those subscribers will not be imported and we'll let you know with a message on-screen:

Important suppression list details

The suppression list only stops matching email addresses from being imported manually or via a list. It will not stop email addresses added or reactivated in the following ways:

  • Via an API call, if you import subscribers that way.
  • Through a subscribe form, if someone resubscribes "organically" using the same email address.
  • As a result of the subscriber’s status being changed from "Bounced" or "Unsubscribed" back to "Active." In this case, they will be sent any emails you send to that list, even though they remain on the suppression list.

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.

Note: If you see "Reason unavailable" it means the email address was added some time ago, before reasons were recorded in the system.