Hello,

I am attempting to setup the following scenario. I have two servers, Server1 & Server2, both have their own public IP address. I want to configure them as such, that if Server1 gets knocked out, then Server2 will take over sending/receiving mail for my LAN clients (All using WinXP with either Outlook 2003 or Outlook Express). Ideally I would like to have it as such that there would be a seamless transfer of control, without any modification to the LAN clients. Each server is running Bind 9 as well (Server1 = Primary, Server2 = Slave). Below is a rough picture to help visualize what I mean.

http://red.epicmarketing.ca/media/mail_system.gif

I would prefer to use Sendmail for the MTA in this scenario, at least until I learn more about how to use Postfix effectively.

Thankyou for any help/tips/suggestions.

wow that *IS* rough huh?

Ideally you should be using MX records to host failover services. By setting MX priorities of say, 0 for your main server and 1 for the secondary a domain can handle relays fine in the event of an outage. Having said that though, you'd use that more on a lan where you aren't specifying an SMTP server directly to the clients. in that case you'd be looking at a much more generic HA setup, using a heartbeat or such like. see http://linux-ha.org for details