Putting a priority setting on your mail servers will make ProtectLink Gateway Email Protection follow a particular order when delivering inbound mail to your domain.
Step 1: To do this, make a hostname that points to multiple mail exchange (MX) records. Your DNS entries should be similar to this:
imhsmail.yourdomain.com. IN MX 10 mailserver1.yourdomain.com imhsmail.yourdomain.com. IN MX 20 mailserver2.yourdomain.com imhsmail.yourdomain.com. IN MX 30 mailserver2.yourdomain.com mailserver1.yourdomain.com. IN A 126.96.36.199 mailserver2.yourdomain.com. IN A 188.8.131.52 mailserver3.yourdomain.com. IN A 184.108.40.206
Note: Contact your DNS technician if you need assistance.
Step 2: We will then configure our Postfix servers to use:
yourdomain.com smtp: imhsmail.yourdomain.com:25
In this setup, our mail servers will try to deliver to mailserver1.yourdomain.com. If unsuccessful, we will try using mailserver2 and so on.
An email will be delivered only to the first server that accepts it and not to all servers.
This is useful when you have multiple locations, because there will still be other mail servers if one becomes unavailable.