Recipient email addresses after a bounce may be added to this suppression list based on the reason for the bounces, suppressions are not based on ‘hard bounce’ or ‘soft bounce’ but based on the reason or the bounces. The function of the Suppression list is to avoid a recurring send to mailbox / user that has bounced. This helps to avoid impact to IP reputation. After expiry of the period the address will be automatically removed.
In order to remove an email address from a suppression list, please create a ticket with Sinch Support.