BaseDirectory           /var/lib/opendkim
Canonicalization        relaxed/simple
SigningTable            dsn:mysql://USER:PASS@3306+127.0.0.1/mailserver/table=virtual_domains?keycol=Name?datacol=ID
Domain                  dsn:mysql://USER:PASS@3306+127.0.0.1/mailserver/table=virtual_domains?datacol=Name
ExternalIgnoreList      refile:/etc/opendkim/TrustedHosts
InternalHosts           refile:/etc/opendkim/TrustedHosts
#KeyFile                 /etc/opendkim/1337.private
KeyTable                dsn:mysql://USER:PASS@3306+127.0.0.1/mailserver/table=virtual_domains?keycol=ID?datacol=Name,Selector,PrivateKey
PidFile                 /run/opendkim/opendkim.pid
#Selector                1337
Socket                  local:/run/opendkim/opendkim.sock
Syslog                  Yes
SyslogSuccess           Yes
TemporaryDirectory      /run/opendkim
UMask                   002
UserID                  opendkim:postfix

Starting OpenDKIM daemon...
opendkim: /etc/opendkim/opendkim.conf: dsn:mysql://USER:PASS@127.0.0.1/mailserver/table=virtual_domains?keycol=Name?datacol=ID: dkimf_db_open():
opendkim.service: Control process exited, code=exited status=78
Failed to start OpenDKIM daemon.
opendkim.service: Unit entered failed state.
opendkim.service: Failed with result 'exit-code'.

# opendkim -v -t opendkim.conf
opendkim: opendkim.conf: line 2: header malformed