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.