how can I unblock my M/S Outlook blocked email

I write to ask if any of you Teck`ies can help me. I have a problem with Outlook Email. When I try to send emails a window pops up asking for user name and password. I have entered the correct password but still as blocked. My wifes email works ok on the same machine also my rarely used second email address. But my main one refuses to work. It is over a week now and my emails must be piling up at the Talk Talk server. I did a Antivirus scan using AVG and it found a trojan horse called agent2 it killed it but my email still is blocked. Any advice would be most appreciated.
Kind regards Glyn