Email Behind Firewall
From mail2web.com Wiki
Can I access my email through a firewall?
Answer:
If your POP3 mail server is outside your firewall and your firewall allows connections to port 80 (used by HTTP/web sites), mail2web.com will work. If you are trying to reach a POP3 server that is behind a firewall, you won't be able to access it unless it has been configured to be accessible by mail2web.com.

