Overview
The backup MX host must accept and queue mails, if the
primary mailhost is down for a certain domain. To have a high degree of
availability the backup MX host must be located outside the backed up
domain. You can setup the backup MX host as a primary or secondary mx for
a remote site.
The primary mailhost is down ...
Email is delivered to the backup MX host and
queued there ....
After the primary mailhost is up and running
again, email is delivered from the backup MX host to the primary mailhost
and stored in the local mailboxes.
Setup of a primary mx host for a remote
site
IN MX 10 mail1.backup1.com. IN MX 20
mail2.backup2.com.
All email for the remote site is delivered to
the primary mx host: mail1.backup1.com.
/etc/postfix/main.cf:
relay_domains = $mydestination
the.backed-up.domain.name smtpd_recipient_restrictions =
permit_mynetworks
check_relay_domains
/etc/postfix/main.cf:
transport_maps =
hash:/etc/postfix/transport
/etc/postfix/transport:
the.backed-up.domain.name
smtp:[their.mail.host.name]
Setup of a secondary mx host for a remote site
IN MX 10 mail1.backup1.com. IN MX 20
mail2.backup2.com.
All email for the remote site is delivered to
the secondary mx host: mail2.backup2.com.
/etc/postfix/main.cf:
relay_domains = $mydestination
the.backed-up.domain.name smtpd_recipient_restrictions =
permit_mynetworks
check_relay_domains |