Backup Mailserver

This is an easy postfix configuration to backup all emails going to specified domains until the master server is online again.

Postfix Configuration [replace yourhostname with your hostname]:

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated reject_unauth_destination
myhostname = yourhostname
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
myorigin = /etc/mailname
mydestination = $myhostname, localhost.yourhostname , localhost
relayhost =
mynetworks = 127.0.0.0/8
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all
maximal_queue_lifetime = 30d

relay_recipient_maps =
relay_domains = hash:/etc/postfix/relaydomains
transport_maps = hash:/etc/postfix/transportmaps

/etc/postfix/transportmaps [how it could look like]

exampledomain.example       smtp:masterserver.exampledomain.example:587

 /etc/postfix/relaydomains [how it could look like]

exampledomain.example OK

 After you have changed the transportmaps or relaydomains file you have to run in console

postmap /etc/postfix/relaydomains
postmap /etc/postfix/transportmaps