How to properly test a mail server?

I've been sending and receiving emails from a few addresses and it seems to work. Just wondering what else should be done to make sure the server(Perfect server - Debian 5.0) will work properly?

 

Well ... since mail servers are generaly used for sending and recieving mail messages I think you have tested it thoroughly

 

Check your mail log for errors or any abnormalities.

 

Thx.

The mail log is fine, the only error is in the ISPConfig Cron log;

...not sure what that is or what it affects.

 

You probably did not set up an account to fetch mails from a remote server. You can ignore this.