Install
# OpenBSD – built-in:
rcctl enable smtpd && rcctl start smtpd
# Other platforms:
# Ubuntu/Debian:
apt install opensmtpd
# AlmaLinux/RHEL:
dnf install opensmtpd
# Arch:
pacman -S opensmtpd
Basic /etc/mail/smtpd.conf
pki mail.example.com cert "/etc/ssl/m...