CentOS 5 :: Open Port For Secure Imap And Smtp ?

The server I'm running is virtually stock CentOS - it's running on a xen virtual host, started as CentOS 5.1 (32 bit) when that was fresh, it's at 5.5 now and updated nightly. All packages except postgresql and php are from CentOS and EPEL.

I'm running dovecot on it, and for long time, squirrelmail connecting via localhost was good enough. All external ports were firewalled by the CentOS firewall (just 25,80,443,custom ssh are currently open).

Now I need to allow an external imap client to connect.

I have generated ssl key and configured the dovecot configuration and it should be good to go, but gosh dangit, I can't remember how to open the port in the configuration.

I did it before when I set up ssh to run on a non standard port after I got sick of constant brute force attack on port 22, but I can't recall what I did and the various tutorials I find online all tell how to do it with the GUI tool, but I don't have any GUI stuff installed.

system-config-securitylevel-tui

Is I'm pretty sure what I used to open up my custom > 1024 ssh port, but I can't remember how I used it to open that port and it doesn't seem intuitive. Also, do I need to use 993? I'd almost rather use something custom above 1024, as long as thunderbird supports it (don't care about any other mail client)

Finally, my smtp server is postfix and port 25 is already open (but not an open relay, I check it about every 3 months). For requests to send mail from a client, I would really like some authentication of some type - as in only relays for IP addresses that have recently successfully logged in the secure imap port.