[TriLUG] email (imap) setup question

[Henryk M. Kowalski]

Sanity/config check needed, please.
Searching on Google didn't turn up much that was of help to me...  :(

I've set up an email server at home.
It's on a DMZ behind my firewall.
Running Mandrake 8.2, postfix and imapd, latest updates on all.

SMTP works fine but imapd was breaking some of my email clients and caused 
long connection delays with others.

Looking at the firewall logs I noticed that each time I tried to login to 
check my email the mail server was trying to connect to my client machine 
on port 113 (auth) and would sit there until it timed out.  Once I opened 
the port to allow the connection the problems with the connection 
went away and my email clients are happy and very responsive.  
I get instant connectivity to my email.

I'm curious, because this (open 113 port) doesn't seem to be necessary 
when accessing other (external) email servers.
What am I missing?
Is my imapd misconfigured?
If so, where/what do I need to change?
Is there a reason to avoid the open 113 port from my DMZ?

Thanks in advance,

--hmk