Newbie Question

I'm trying to install 2 lotus servers one will be set has a backup server and also trying to add a third pop3 or sendmail server so users can receive their email via lotus or the other mail servers and if lotus crash or I decide to stop using it, it won’t affect the other mail servers and the users will still receive their email..

Would like to know if that something possible and if so how to do it
I use slackware and redhat.