Connecting windows mail to web mail through LAN

Hi

I got an error when trying to connect to external mail through LAN
using web mail (Vista). Everything is ok if I connect through dial up
connection. We are suing ISA proxy. The error is:

The connection to the server has failed. Account:
'mail.bnreducation.com', Server: '76.162.254.61', Protocol: POP3,
Port: 110, Secure(SSL): Yes, Socket Error: 10060, Error Number:
0x800CCC0E
The host 'pop3.omantel.net.om' could not be found. Please verify that
you have entered the server name correctly.
Account: 'pop3.omantel.net.om', Server: 'pop3.omantel.net.om',
Protocol: POP3, Port: 110, Secure(SSL): No, Socket Error: 11001, Error
Number: 0x800CCC0D

Any one knows how to solve such thing?

Bye

Wail