With the new OpenSMTPD syntax change which landed with OpenBSD 6.4
release, changes are needed for making opensmtpd to act as a lan relay
to a smtp server. This case wasn’t covered in my previous article
about opensmtpd, I was only writing about relaying from the local
machine, not for a network. Mike (a reader of the blog) shared that it
would be nice to have an article about it. Here it is! :)
A simple configuration would look like the following:
listen on em0
listen on lo0
table aliases db:/etc/mail/aliases.db
table secrets db:/etc/mail/secrets.db
action "local" mbox alias <aliases>
action "relay" relay host smtps://myrelay@remote-smtpd.tld auth <secrets>
match for local action "local"
match from local for any action "relay"
match from src 192.168.1.0/24 for action relay
The daemon will listen on em0 interface, and mail delivered from the
network will be relayed to remote-smtpd.tld.
For a relay using authentication, the login and passwords must be
defined in the file /etc/mail/secrets like this: myrelay
login:Pa$$W0rd
smtpd.conf(5) explains creation
of /etc/mail/secrets like this:
touch /etc/mail/secrets
chmod 640 /etc/mail/secrets
chown root:_smtpd /etc/mail/secrets