I have a question regarding the message_drop_headers main.cf configuration parameter.
The man page states that it:
“[specifies] names of message headers that the cleanup(8) daemon will
remove after applying header_checks(5) and *BEFORE* invoking Milter
Checking man 8 cleanup I note this relates to:
“...inbound mail...inserting into incoming mail queue...”
On the smtpd(8) server process, I have OpenDKIM configured to run as a Miller. It currently notifies me in the log if DKIM signatures on incoming mail were found and if it was able to validate them.
BUT . . . If message_drop_headers is extracting some header information *BEFORE* running the OpenDKIM Milter, how is it that DKIM is not breaking ? Isn’t that discarding header information that would be used in computing the DKIM signature ?