that can be used to create a redundant mail server environment. Depending
on what you are trying to accomplish one of the two configurations outlined
below will allow you to either set up
environment so no mail is lost
if any downtime occurs, or so
mail throughput has no downtime due to any server problems. Both of the
configurations can be implemented together so as to obtain the desired affects in one environment.
1. Store Mail While Primary Server is Offline:
below, shows how to configure an MX record to have a backup
This will mean
that if the primary mail server is offline, that the secondary backup MX will
accept the e-mail on behalf of the primary.
To do this, configure the secondary
MX mail server with all the domains to host, and use the smart host option for
each domain, or in the SMTP service properties so that it is directed
to the primary MX mail server. This way, if the primary goes offline, then the secondary
will accept the mail, and queue it until the primary server is back
2. Server Redundancy
redundancy, whereby if one server goes offline, then the other will totally
assume the role of the primary, configure the two servers in a cluster rather
than using the smart host option. This way both servers share the same message
store and queues and so long as the message store/queue repository is online,
messages will be delivered accordingly.
This will also
require a clustered IP address for any clients and other servers to connect to.
There are many network load balancing switches available on the market that will
do this. The MailEnable
Enterprise Infrastructure Configuration Guide outlines this approach in
configure back up or redundant mail servers: