I created a client library to send emails for a webapp.

After connecting to the SMTP server with credential setup in CPANEL, and then do NOT add Message-Id header, the DKIM signature 'h' record created by dovecot/WHM is wrong, and a Message-ID (with a capital D) header is added, invalidating the generated DKIM signature value.

This causes outlook, yahoo, gmail and other email recipients to add 'dkim:fail' to the message, and thus relegate it to junk or spam.

The work around is to add to the message a Message-Id with a  little ‘d’ header.  Then the SMTP server processes the email with the correct generated DKIM, correct DKIM ‘h’ record and does not add a Message-ID header.

My SMTP hosting providers that run the WHM/dovecot/CPANEL software are refusing to raise this as a bug and have requested that I do it.

Regards

Robert