When a user unsubscribes from a database, the contact email address is added to the database suppression list. Apart from this Suppression can also happen for other reasons, such as an address including a domain or prefix that is on the email blocking list or an address that is on the global suppression list that means clients do not have access to this list.
Clearalist Email List Cleaning Software easily inspects pre-email-level suppression list to remove bad emails cause if a contact’s email address is on a database-level suppression list, he or she will not get emails from that selective database.