Not to lose mails when main mail server is down, best solution is – mx backup server.
This is configuration to have backup mx server set up and running.
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myhostname = mx2.loginroot.com
mynetworks = 127.0.0.0/8
maximal_queue_lifetime = 120d
smtpd_banner = $myhostname ESMTP
relay_domains = hash:/etc/postfix/relaydomains
transport_maps = hash:/etc/postfix/transportmaps
smtpd_recipient_restrictions =
permit_mynetworks,
reject_unauth_destination
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create /etc/postfix/relaydomains with contents:
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loginroot.com OK
otherdomain.tld OK
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then to create map for postfix – run:
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postmap /etc/postfix/relaydomains
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create /etc/postfix/transportmaps with contents:
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loginroot.com smtp:mx1.loginroot.com:25
otherdomain.tld smtp:primary_mx_server:port
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and run:
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postmap /etc/postfix/transportmaps
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Backup MX should be added in DNS zone in order to receive mails.
In my case I have such records:
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% dig mx loginroot.com +short
10 mx1.loginroot.com.
20 mx2.loginroot.com.
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First digit means priority. The bigger value, the smaller priority.
So my MX backup server is mx2. It receives mail only if higher priority server is down.
That’s it.
