DKIM fail if WHM adds Message-ID, should be Message-Id

[webadmin at exalt.com.au]

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

When the client library makes a connection to the SMTP server, and  
then do NOT add Message-Id header,  Message-ID (with a capital D)  
header is added, and the SMTP server adds a incorrect DKIM-Signature  
record 'h' part, invalidating the generated DKIM signature value.

This causes outlook, yahoo, gmail and other email recipients to add  
'dkim:fail' to the message which pushes it into junk/spam folder.

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  
DKIM-Signature, correct DKIM ‘h’ part and does not add a Message-ID  
header.

Message-ID fails DKIM, Message-Id is better by OzBob · Pull Request  
#142 · dovecot/core (github.com)
https://github.com/dovecot/core/pull/142

Regards
Robert