Server is not receiving external emails

[gawry]

I have a different setup from the usual Perfect server. What i've done was a mix from the Installing a multple ISPConfig server on Debian Lenny Howto and Debian Squeeze Howto

1 Main Web server (where is ISPConfig panel)
1 Mail server - Postfix, courier, roundcube with lighttpd
1 Secondary Web server
1 MySQL Server - Running phpmyadmin with lighttpd

I can send emails to any email but I can only receive from internal email addresses. Why does is this happening

some emails returned couple days later.

Delivery to the following recipient has been delayed:

email@domain.com

Message will be retried for 2 more day(s)

Technical details of temporary failure:
The recipient server did not accept our requests to connect. Learn more at http://mail.google.com/support/bin/a...py?answer=7720
[domain.com (1): Connection refused]