There's a thread here which explains what is going on: http://forums.mozillazine.org/viewtopic.php?f=39&t=3001787 I know it looks technical (tho I'm not a technical person!) but two points are being made: 1) If you want to use POP mail you now have to log in to outlook.com and 'enable' POP. (See the final post in the thread.) If you don't do that you will get the error message you have received. 2) The reason you have to do that is because Outlook (like many other mail providers) is making IMAP rather than POP the default. If, in the light of that, you now want to switch your account from POP to IMAP, follow the tutorial here: https://support.mozilla.org/en-US/kb/switch-pop-imap-account