Suppressions are a mechanism that Mailgun utilizes to ensure that delivery is prevented to addresses that are problematic for various reasons. Without Suppressions to prevent further sending to these problematic addresses, your domains would incur AUP violations such as high bounce rates and complaint rates, which in turn negatively impact your email deliverability. There are three types of Suppressions:
- Bounces (when a recipient's address is invalid/non-existent)
- Unsubscribes (when a recipient no longer wishes to receive emails)
- Complaints (when a recipient considers the messages as spam)
The Suppressions can be viewed either in the Suppressions or Logs tabs of the Mailgun Control Panel or programmatically through the relevant APIs (i.e. the Bounces, Unsubscribes, and Complaints APIs).
Concerning bounces, the Suppressions page will list the address, the date the bounce occurred, and the error the recipient's email server returned that prompted our system to add the address to the Suppressions.
Whereas for unsubscribes, the Suppressions tab will list the address, the date the unsubscribe was received, and the details such as "*" for a domain-wide unsubscribe or a specific Tag value for a campaign-based unsubscribe. (Note: subscription status of a member in a Mailing List is indicated in the Mailing List section of the Control Panel).
Finally, for complaints, the Suppressions site will list the address, the date the complaint was received, and the details column is not used for complaints.
As addresses accumulate in your Mailgun Suppressions, we recommend a best practice of regularly removing those addresses from any contact lists that you maintain. This will ensure that you are no longer sending to these addresses through your sending application. To be clear, the addresses should be removed from your contact lists - wherever they may be stored (e.g. CRM, database, file, etc) - and not from the Mailgun Suppressions.
For other best practices such as our list management practices, subscribe handling practices, and feedback loops and spam complaints practices please see our Email Best Practices documentation. Additionally, you may also want to consider using our awesome email validation service to ensure your lists are not overflowing with invalid email addresses (low bounce rates FTW)!