CentOS - Jan 2012 - Confusion over sendmail and smtp auth on a 6.2 server

I'm reading a lot on how to setup my smtp auth on a new Centos 6.2 
server. I want to use sendmail and have this running on a Centos 3 
machine now, so it's not new stuff to me.

Unfortunately, the more I read, the more confusion I seem to have. 
Firstly, how to generate my certificates. A good recommendation or howto 
would be in order. I think most of the confusion here comes from the 
commented names of files used in sendmail.mc for all the auth files. As 
far as I can tell, the encryption length is the only change I need 
(going to a minimum of 2048 bits) from the old system generation. Those 
"pem" files throw me a bit, though.

Secondly, I'm reading DoveCot has a problem with security and that I 
need to run something other than ? (Cyrus, Courier, etc) to make this 
work. I typically don't run imap security, only on smtp, so I'm not sure
if there's to be interference between the two. Since postfix is the 
default now on Centos 6.2, what should I look for by changing it back to 
sendmail when it comes to smtp auth?

I only authenticate users that are not in the building on our network to 
allow them to send email. They're free to use pop or imap to retrieve 
their email without authentication.

Thanks for any clarity on this.

steve campbell