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When it comes to email marketing, your suppression list is essential! Not only to maintain your sender reputation but to comply with the CAN-SPAM act’s requirements for commercial messaging.

The suppression list consists of recipients who have unsubscribed from your mailing list, who have made a spam complaint and, of course, is a collection of those recipient addresses that caused a hard-bounce, such as a blocked or invalid email address.


When a recipient unsubscribes from your mailing list, they should be added automatically to a suppressions list within your email client, or removed from your mailing list, to avoid further emails being sent to that recipient. By solely adding an unsubscribe footer to your email, your job is not done! You need somewhere for those unsubscribes to go: the suppression list. This also counts for spam complaints and hard-bounced recipients 👇, they come hand-in-hand. If they are not automatically added to a suppression list, they must be removed from your mailing list altogether – and fast!

Spam complaint

Don’t make the terrible mistake of sending further emails to recipients who have marked your email as spam. It can cause irreversible damage to your domain and IP’s reputation. Internet Service Providers (ISPs) know more than you may perceive. If you think you can get away with it, think again! ISPs will recognize that you are continuing to send to recipients that DO NOT want to receive your email (really, what’s the point?!), and you’ll be penalized for irresponsible sending with a blacklisted IP or domain.


Alongside unsubscribes and spam complaints, your suppression list will contain recipient addresses that caused a hard-bounce. A hard bounce is a permanent error, such as an invalid email address, as opposed to a soft-bounce, which is temporary. Again, it is really important to ensure you don’t keep sending emails to these addresses. Although you won’t directly annoy a recipient (as the recipient doesn’t exist), ISPs will spot that you’re not cleaning your mailing list on a regular basis and see you as an irresponsible sender.

How SMTP2GO helps you keep on top of suppressions!

At SMTP2GO, we automatically handle a suppression list for you. When a recipient unsubscribes, makes a spam complaint, or causes a hard-bounce, they’ll be added automatically to a suppression list within your SMTP2GO account. We often recommend removing the recipient from your mailing list as well, but you won’t need to worry about further emails being sent to that recipient. As long as they remain on that suppression list, emails will be blocked and show as “Rejected”.

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