POP3 problem

I have a small business server (win2003 SP3)
and a SonicWall TZ170W as my router.

I already have a SMTP service running well on the server.

But i can’t get de POP3 service running.

From the LAN i can connect to POP3 but i can’t reach it from de internet.

I had SonicWall support to check if everything is ok on the router,.

please need help.