I recently migrated a server from Ubuntu 14.04 to one running 18.04 but with the same mail setup. I simply copied over Postfix's main.cf and the contents of /etc/mail/opendkim over.
The server is sending mail to a remote mail host over the LAN without problems. However, opendkim refuses to sign the emails as it was before.
My postfix.cf file:
myhostname = host.domain.com myorigin = $mydomain relayhost = 10.10.10.105 inet_interfaces = loopback-only mydestination = milter_default_action = accept milter_protocol = 6 smtpd_milters = inet:localhost:8892 non_smtpd_milters = inet:localhost:8892 compatibility_level = 2
Syslog yes UMask 007 Socket inet:8892@localhost PidFile /var/run/opendkim/opendkim.pid OversignHeaders From UserID opendkim Canonicalization relaxed/simple KeyTable /etc/mail/opendkim/KeyTable SigningTable /etc/mail/opendkim/SigningTable ExternalIgnoreList /etc/mail/opendkim/TrustedHosts InternalHosts /etc/mail/opendkim/TrustedHosts
The TrustedHosts file contains both the IP and the host name of the sending machine (and hostname -f is correct). Both machines are on the same domain.
I see no errors in either the sender's logs or that of remote mail host. If I shut down the opendkim daemon on the sender, I see postfix complain that it can't connect to the opendkim socket.
I have tried setting the milter_protocol to 2 (it was originally 6) but that has no effect.
Looking at the headers on the mail received from the affected host, there is no mention of dkim.