If you run e-mail server system by one server, not use redundant setup, you may have risks about can't receive/send e-mails.
This article describes how to configure redundant e-mail server to avoid problem.
Run following command to install Postfix on secondary server.
# pacman -S postfix
After installed, begin setup.
/etc/postfix/main.cf by following.
myhostname = secondary.hoge.net mydomain = hoge.net myorigin = $mydomain inet_interfaces = all mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain relay_domains = hoge.net transport_maps = hash:/etc/postfix/transport alias_maps = hash:/etc/postfix/aliases alias_database = $alias_maps smtpd_banner = $myhostname ESMTP unknown disable_vrfy_command = yes smtp_sasl_auth_enable = yes smtp_sasl_password_maps = hash:/etc/postfix/relay-password smtp_sasl_security_options = noanonymous smtpd_helo_required = yes smtp_tls_security_level = may
Append following line to
Wrap hostname by
 is for avoiding search by DNS MX records when transferring e-mail.
After editted transport file, refresh by running follow command.
# postmap /etc/postfix/transport
Append follow line to
user with e-mail account registered at primary e-mail server.
After editted aliases file, refresh by running following commands.
# postalias /etc/postfix/aliases # newaliases
Create password configuration file to access primary server e-mail account.
This configuration is needed because primary server e-mail account use SMTP Auth.
/etc/postfix/relay-password as root privileges and add follow line.
[primary.hoge.net]:587 user:Input user's password
After editted, modify privileges to avoid reading/editing this file without root.
# chmod 600 /etc/postfix/relay-password
Refresh by running follow command.
# postmap relay-password
Redundant setup is completed. Open postfix-related port(e.g. 465, 587) on firewall. And also add
secondary.hoge.net MX record to DNS with greater priority value than primary server.
After that, run following commands to start Postfix, and auto start when system startup.
systemctl start postfix systemctl enable postfix
Redundancy setup is completed. Received e-mail is pooling to secondary server when primary server is down, and retry transporting e-mail to primary server in 5-days. This period can adjust by preferred value you want.