[CentOS] how do I install mailman in a mail cluster

I am trying to figure out the best way to install Mailman, or any other mailing list software in a mail cluster, i.e. two postfix smtp gatways, two squirrelmail webmail servers, failover cyrus imap servers..

I initially installed it on the same machine as the imap server since this is where the mail ends up and only is delivered through one machine.

I have other just technical kludges, like propogating the mailman aliases to the smtp gateway so that it knows what is a local user. i.e. the smtp gateways check ldap to see if a local destination is actually valid before sending the mail to the cyrus mailstore via a postfix relay...

How are other people solving this ?