No Hair Github Pages: OpenBSD Mail Server Notes

Setting up a mailserver on OpenBSD 6.9: OpenSMTPD

E. Preliminary configuration and testing of OpenSMTPD

1. At this point, we might should go ahead and install all the other packages needed:

pkg_add opensmtpd-extras opensmtpd-filter-rspamd dovecot dovecot-pigeonhole rspamd redis

2. OpenSMTPD is installed in base. First, copy the default smtpd.conf:

doas cp /etc/mail/smtpd.conf /etc/mail/smtpd.conf.default

Then create your new smtpd.conf like so:

# smtpd.conf

# PKI keys for TLS
pki mail cert "/etc/ssl/mail.example.com.fullchain.pem"
pki mail key "/etc/ssl/private/mail.example.com.key"

# Tables
table aliases file:/etc/mail/aliases
table credentials passwd:/etc/mail/credentials
table virtuals file:/etc/mail/virtuals

# Listeners
listen on all tls pki "mail" hostname "mail.example.com"
listen on egress port submission tls pki "mail" hostname "mail.example.com"

# Actions
action "local_mail" mbox alias <aliases>
action "domain_mail" maildir "/var/vmail/example.com/%{dest.user:lowercase}" \
	virtual <virtuals>
action "outbound" relay

# Rules

# Local
match from local for local action "local_mail"
match from local for domain "example.com" action "domain_mail"
match from local for any action "outbound"


# Remote
match from any for domain "example.com" action "domain_mail"
match from any for any action "outbound"

We'll flesh this out after dovecot and rspamd are set up.

3. Check configuration and restart smtpd:

doas smtpd -nf /etc/mail/smtpd.conf
doas rcctl restart smtpd

4. Check if it's working by sending messages from a local user to domain address:

mail -s "Test mail from local user" john@example.com
John,
This might work.
Cheers
ctrl-d

Check if the mail is received:

doas ls -al /var/vmail/example.com/john/new/

Once you're sure that it works, go ahead and stop smtpd because this configuration allows your server to be an open relay. We'll finish up OpenSMTPD configuration later.

Next: PF configuration

Previous: Virtual users

Posted by Gordon, No Hair Github Pages, August 24, 2021