I'll try to be as specific as possible, but I'm new to all of this.
Okay, my set-up:
1) iMac connected to a wireless router (Netgear WGR614) with DSL connection.
2) DynDNS.org dynamic DNS account with DNSUpdate software.
*3) Router set-up to forward all external request for SMTP(port 25) and IMAP(port 143) to my local IP address. This is how external mail request get to my computer through the router.*
4) Panther firewall has the same ports open.
5) Postfix Enabler settings:
-----Send mail tab: admin username placed in "admin" field, the rest default.
-----Mail server tab: dyndns.org address in "domain name" field, the rest default.
-----The rest of the tabs I have left alone for now.
-----Obviously I've clicked the "Enable Postfix" and "Enable IMAP" buttons.
If I did anything else special, it was either accidental or I'm simply not remembering it. I can say that machines outside my local network were not able to connect and use the server until I assigned the proper port porwarding settings in the router.
I hope this helps. Like I said, I'm no expert here. I just needed to set-up postfix to test some PHP apps I'm developing, and I got off on a "be my own e-mail provider" tangent.
d8n_two