Hello,
if you want to be fully green with mxtoolbox, then do this:
cp /var/lib/pmg/templates/main.cf.in /etc/pmg/templates/
Edit the file /etc/pmg/templates/main.cf.in
and replace this:
myhostname = [% dns.hostname %].[% dns.domain %]
to this to the fqdn you need:
myhostname=mail.domain.com...