Sarje | Nov 14 2007 1:15PM GMT
It depends on Authentication type set on smtp virtual server one exchange server and settings on email client (is it Exchange mailbox, POP3 mailbox, IMAP4)
look it for Anonymous access. also do telnet from client side if it successfully done. Also try another email client Thunderbird, evolution, kmail and try out
Occasionally, some anti-virus programs may cause problem. If you’re using one, try to disable it temporarily and do the test.