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Introducing custom email headers

This feature is available for accounts on the new Google Cloud infrastructure.

Headers are a critical part of an email. In a nutshell, they describe the message content and its behavior: where it’s coming from and where it’s going. The common ones are To, From, Date, and Subject, but headers can be customized to do a great many things: tag emails, track them, or control specific behaviors. Now you can do that in!

What’s it look like?

When you’re composing your email, you can add or remove a custom header super-easily:

Add with the 'Add custom headers' option in the Composer
Add with the ‘Add custom headers’ option in the Composer
Remove headers
Remove using the ‘X’ button

You’ll see how many there are with the label next to the heading. You can add up to ten and collapse (or open) them, with the arrow on the right:

Collapsed headers
Ten custom headers, collapsed. Click the arrow to “un”-collapse!

That’s the quick run-down— we look forward to seeing how you level up your sending with custom headers! A few things we’ve heard before:

  • Set the X-Mailgun-Tag header, for those using Mailgun’s “Topic” subscription functionality
  • Customizing the List-Unsubscribe header
  • Use X-Entity-Ref-ID to stop Gmail showing emails as a thread
  • Use X-Auto-Response-Suppress:OOF to suppress auto-replies from Exchange servers

A quick note

This is a fairly advanced feature and we want to make it as useful as possible. If you need a hand, we’ve got more detailed documentation for you on the feature, as well as on the errors you might see.

As always, if you have any questions or feedback on this feature, please let us know!