From: Bill Cole (postfixlists-070913billmail.scconsult.com)
Date: Sun Jan 06 2008 - 20:23:48 CST

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At 12:29 AM +0100 1/7/08, Carlos Jiménez wrote:

[...]

>Do you think it is better to use two MX than using one MX and a load
>balancer with two Postfix Servers?

Absolutely.

Load balancers were invented to deal with HTTP,
where the protocol provides no model for
automatic client failover and every connection
failure is immediately exposed to the end user.
As Dr. Venema noted, SMTP is a very different
thing.

>We thought in the load balancer because the customer had it (and he wanted
>to use it) and thinking on redundancy capabilities with this device.

Think about that more carefully. If you only have
one load balancer, using it reduces your
redundancy because you are imposing a single
point of failure.

>Also,
>it was easier for the customer to redirect all outgoing SMTP traffic to one
>"Virtual IP" than configuring any kind of load balancing (to the IP
>addresses of Postfix Servers) in their back-end Mail Server (Lotus Server).
>I'd appreciate any suggestion.

The outbound gateway function is a different
circumstance from inbound "MX" function. The
right sort of load balancer setup (e.g. 2 load
balancers rigged for failover) can be useful for
an outbound gateway system when you cannot count
on all of the mail sources using it to do the
right thing when given a name with multiple A
records in DNS.

--
Bill Cole
billscconsult.com

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