I have a Mail Server on my LAN (through my ISP)

I can send mails to an outside address but can't receive from an outside address.

Now, my ISP is blocking all lower ports (upto port 1024)

Is there a way to redirect all incoming mails to my ISP's POP3 so I can download them using my Mail Server ???

I know that "NO-IP" offers this service called "Reflector" but you have to pay.

Does someone knows a free service for this ???