Personalized custom email header fields

Your software
My Mautic version is: 5.0.3
My PHP version is: 8.1
My Database type and version is 10.5.23-MariaDB-0+deb11u1 - Debian 11

Your problem
My problem is:
I want to add custom email header fields and personalize it. For example,
x-user-id: 1111111 for one email
x-user-id: 2222222 for another email

I can’t find a way to do that.

Are you saying you want to place the contact id token in the custom header?
Did u try in email > advanced tab?

There’s two ways to do this. You can do it globally:
Settings → Configuration → Email Settings → Custom Headers → Add Value

Or by individual email:
Channels → Emails → Select the Email → Edit → Advanced → Custom Headers → Add Value

Thanks! That works!

Thanks! It helps!