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Understanding Mailgun Suppressions (Bounced, Complained, Unsubscribed, And Whitelisted)

Suppressions are a mechanism Mailgun utilizes to help ensure the protection of your domain's reputation, as well as the reputation of our IP's. Specifically, this is all about internally preventing delivery to addresses that have been demonstrated as problematic for various reasons.

Since they've been proven to encounter issues with receiving mail from your domain in a way you certainly don't want repeated, we internally block sending to these addresses so they don't harm your ability to keep sending. Without Suppressions to prevent further sending to these particular addresses, your domain would run into AUP violations such as high bounce and complaint rates, severely damaging your email deliverability; exactly what we don't want!

How are Suppressions Organized?

Suppressions are organized per domain, since they're based on the proven interaction with a specific send. To view Suppressions, you can either use the Mailgun control panel or view programmatically through the relevant APIs (see below, under Types of Suppressions). In addition to just viewing your current Suppressions, you can add/delete single addresses, or even entire groups of addresses. We'll show you how to do this below:

  1. First, log in to the Mailgun Control Panel (if you have not already done so).
  2. Then, within the left-hand navigation pane, click the Sending option to expand its list of suboptions.
  3. Next, click the Supressions suboption. You can either view all Suppressions for that domain by default or search for a specific address via the blank on the right.

Types of Suppressions

There are three types of Suppressions; Bounces, Unsubscribes, and Complaints as well as a Whitelist functionality.

  •  Bounces - These aren't just any bounces/failures; rather, these are those bounces that specifically happen due to a recipient's address being returned as invalid/non-existent/temporarily misconfigured.

When viewing the Bounces portion of the Suppressions page in the Mailgun control panel, the page will list the address, the date the bounce occurred, and the error message the recipient's email server returned that prompted our system to add the address. This way, you see exactly why the address was added to the list. You can also pull these results via the API.

  • Unsubscribes - Pretty simple; when a recipient no longer wishes to receive emails, and has clicked to unsubscribe.

With 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). Or, you can use the API.

  • Complaints - Also simple; when a recipient complains about your sending by clicking to mark it as spam in their inbox.

Next, for Complaints, the Suppressions site will list the address and the date the complaint was received; the details column is not used for complaints. To use the API, refer here.

  • Whitelists - For any email addresses, or domains, that are whitelisted, Mailgun will attempt delivery to such a recipient, even if the recipient is currently registered in the Bounces list.  

Finally, the Whitelists tab will show the recipient, type (email address or domain), and the timestamp of when the recipient was added to the list.  Like the above, results can be polled viz the API. Please note: if a recipient is registered in the Complaints or Unsubscribes lists, Mailgun will not attempt delivery, even if the recipient is registered in the whitelist. As such, when continuing to have an issue with an email address bouncing and becoming suppressed, adding the email address to the whitelist may be beneficial.

Best Practices

As addresses are added to your Mailgun Suppressions, we highly recommend regularly removing those addresses from any contact lists 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. If you just remove the addresses from Suppressions list in Mailgun, and not from your contact lists, the process starts over, and you're again risking damaging your reputation.

For other best practices such as our list management practicessubscribe 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 excellent email verification service to ensure your lists are not overflowing with invalid email addresses from the start. This way, you're using Suppressions in the most effective way possible. Always best to stay ahead of the game!

Got Questions?

Mailgun by Sinch has answers! If you have any concerns or questions, please send us a Support ticket using the Support page within your Mailgun Control Panel.  Our Support Team will be happy to assist!