What happens when you attempt to send outgoing email? Any error messages – or does it simply not function?
are you the only person having the same issue, or is there anyone else having the same problem too? maybe you need to check your outgoing settings on your outlook and the best way is to compare it with your friends (if you are working for a company)
Check with your network admin. Maybe they changed the e-mail server without your knowledge and you might have a setting that is no longer valid. If possible try logging on to another PC with a working e-mail system (under your network signon) and see if you can access your e-mail. This will show whether it a hardware issue (your PC) or a Profile issue.