can't recieve emails with attachments
 

I'm a relatively new user of Linux, have Mandrake 9.1 installed and has been stable for months. I recently installed a gateway/router to enable VPN tunneling between the Linux box and a windows XP computer. The tunnels were set up fine but now users can't seem to recieve emails that have attachments. I have turned off the 'advanced' firewall protection on the gateway and enabled port forwarding for ports 80, 22-25 and 110 (HTTP, SMTP, Telnet, POP3). The mail client is outlook and server is sendmail.

This problem has enluded me for about a week and is really testing my patience. Can I also ask that people replying please be patient with me as I am a windows migrant and still learning. Got a good grasp of Webmin though if that counts as anything!

Thanks in advance

Grant