[Dovecot] How to tell dovecot to use a specific MTA

Hello again people,

OK. I checked a lot of HOWTOs and documents. One specific document describes how one can make dovecot "talk" to postfix. The procedure is pretty straightforward (taken from the document) :

-- . Configuring Postfix and Dovecot

Turn off sendmail:

service sendmail stop chkconfig sendmail off

system-switch-mail (select postfix)

This is for CentOS systems. My question is pretty simple. How exactly does someone tell dovecot (or the CentOS system) that the MTA used is not a pre-packaged postfix MTA but (in my case as you have pretty much discovered by now) XMail compiled from source (no pre-packaged version AFAIK for CentOS; but even if existed, I would still build it on my own) ?

Any help would be appreciated,

Regards,

spyros