its a bug with outlook, get a decent mail client and you wont get the problems, it happens to my account every few weeks at work (dedicated intranet with all mail served by outlook) and when i used outlook at home it would periodicallydevelop the fault as well then clear itself, i was told by the mail server admin the problem is caused by outlook not beign able to authenticate properly when connecting to the mail server, sometimes it would clear with a reboot sometimes it would clear by forcing the process to end (task manager) and then restartign it after all the other boot processe's were completed. but the main fix was to get it removed from startup and manually open the program after login/boot were completed although it would still happen from time to time when it tried to sync with the mail server.
the best thing i did at home to fix the problem was uninstall outlook, and download and setup livemail which looks similar works almost the same and doesnt suffer from the password bug of course you amy find a differnet mail client is more suited to yourself and a lot of people rate thunderbird, i guess that personal preferance 😛
Retyping my user name with the full firstname.lastname@example.org fixed the problem for me tonight. Many thanks tjrad