Can you give me some direction for wikis?

So, thanks to this forum and the great people in it, I was finally able to get my email server up and running... at least some of it. Through Postfix and Dovecot, I can now send maill to myself on my system and then read it through IMAPs on my Apple Mail program. AWESOME!

but... when I try to send emails from somewhere other than my server to the server accounts, I get no joy :(

Is there a seperate setup for this, or do I not have something configured correctly to accept the mail? My DNS (MX) entries are all pointed to my server.

thanks!