This post is about how to make maling lists in OpenBSD (whose current version is 6.5.)
With OpenSMTPD (and Dovecot, optionally), this method is perhaps the simplest.
Add a line for the list to /etc/mail/users like:
[email protected] some_user
...
[email protected] nobody
...
[email protected] vmail
...
+ [email protected] [email protected], [email protected], ...
where /etc/mail/smtpd.conf is:
table domains file:/etc/mail/domains
table users file:/etc/mail/users
listen on lo0
listen on egress \
tls pki <pki> \
auth-optional \
tag MTA
action "local" maildir alias <aliases>
action "domains" lmtp "/var/dovecot/lmtp" rcpt-to virtual <users>
match tag MTA from any for domain <domains> action "domains"
match from local for local action "local"
and also /etc/mail/domains is like:
target.address
ml.address
Compliting the configuration, emails sent to “[email protected]” are forwarded to “[email protected], [email protected], …” directly.
Without any additional servers, it has no functionality such as editing subjects or bodies, but is perhaps the simplest.