I recently came across this problem for a network we provide support for at work, there were not that many solutions for it out there on the world wide web as far as I could see so I thought I would write up what I found:
Password prompt keeps popping up even though the password is saved on the system. Real pig of a problem, Outlook 2002 had same issue but Microsoft fixed, however, when 2003 came out the same issue arose again (possibly only in xp I don't know). A few solutions online including this one and this one recommend messing around with registry keys but personally I am loathe to messing around with registry keys especially on remote desktops for clients when I am connecting on a slow vnc connection.
Luckily there are other things we can try first.
Unecessary authentication?...
First try looking at the settings for the email account:
tools->accounts->settings (or something similar)
If it is not needed then make sure both the:
- log on using secure password authentication and
- smtp authentication
are off. Try again after this.
Some other mystery?...
Still not working? Delete the users account - don't worry this shouldn't delete all the emails in the account, but in case you want to take a backup as I did go to...
C:\Documents and Settings
Look for the folder of the user, can't find it? Go into Tools->Folder Options->View. Make sure you can see hidden folders [Show hidden files and folders -ON].
Still not there?...
Go to Start->Run->cmd to open command prompt. Type in the command 'set'. USERNAME and USERPROFILE should be right at the bottom, the userprofile one is the folder we want to find.
So once you have found it go into Application Data (making sure you can see hidden folders again)->Microsoft->Outlook and there should be a .dat file in there. That is the one you want to copy and backup and if the shit hits the fan put it back in this folder to get the emails back (in theory).
So after all this take note of the settings on the users account like pop3/smtp/username/password and don't forget advanced settings like how long to leave messages on the server etc. Then delete the account, maybe close the program down to be on the safe side, and re-add the account again.
If neither of these options work you are going to have to resort to editing registry keys with regedit or the command regedt32, be very careful and always backup (export) a key before messing around so that you can reload it later.