Suppression Groups

Defining an Unsubscribe Group When Sending

The method used to specify an unsubscribe group for an email depends on how you will be sending that email:

  • When sending an SMTP message, add the group's ID to the X-SMTPAPI header.
  • When sending an email via the Web API v2, add the group's ID in the x-smtpapi parameter.
  • When sending an email via the Web API v3, define the group's ID in the asm.group_id parameter.

You may only specify one group per send, and you should wait one minute after creating the group before sending with it.

When passing asm_group_id please make sure to only use integers as shown in our examples. Any other type could result in unintended behavior.

  "asm_group_id": 1

Defining Unsubscribe Groups to display on the Manage Preferences page

To specify which groups to display on the Manage Preferences page of an email, add the group IDs to the X-SMTPAPI header of an SMTP message, or in the x-smtpapi parameter of a mail.send API call. If you omit the asm_groups_to_display header, your default groups is shown on the Manage Preferences page instead.

You can specify up to 25 groups to display.

  "asm_groups_to_display": [1, 2, 3]


You can find your group IDs by looking at the Group ID column in the Unsubscribe Groups UI, or by calling the GET method of the groups resource.

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