Email headers

We generally leave any header that you add to your message intact in the outbound message. We do, however, remove any Contactlab-specific header that matches the X-Clab-(.*) expression. As a result, you should ensure that you never create custom headers for your own use with a key that matches this expression.

The following headers are always added by Contactlab:

• List-Unsubscribe
• List-Id
• X-Abuse
• X-Mailer
• X-Clab-Family
• X-Binding
• DKIM-signature

Note:

Emails sent to gmail.com recipients have two additional headers:

• A Feedback-ID header
• A second DKIM-signature using d=gmail.clab-fbl.net
  This is needed to enable the Gmail aggregated feedback loop.