I am attempting to set my own value for the message-id header in
emails
delivered via ActionMailer.  The underlying TMail object allows the
message_id to be set, but it looks like the deliver method of action
mailer will overwrite any value that is presently there at the time of
delivery.

Looking at action mailer's base.rb file, you can see that the
perform_delivery_smtp method calls the ready_to_send method, which
calls
add_message_id, which definitively sets the message_id property to the
result of TMail::new_message_id.

Has anyone figured out a way to use their own message ids without
modifying the action mailer code?