A pc with windows XP and outlook 2007 used to connect to office 365 suddenly stopped working, Outlook was left open and logged in over night, when checked in the morning outlook had disconnected and was asking for password. When the password was then entered it wasn't accepted. No updates had been applied over night. As I'd had a similar issue last year which was fixed by running the office 365 desktop setup I ran it again to check for updates and installed any that were needed. Still wouldn't log in. so I upgraded to office 2010, re-ran the office 365 desktop setup, installed the required patches and updates and let it configure what it could. It told me that outlook needed configuring manually. Tried configuring a new outlook profile both with autodiscover and manually and both fail. When setting up the outlook profile " establish network connections" and "search for email@example.com server settings" are successful but log in to server fails. It asks you to check the name and when you do you get "the name cannot be resolved. the microsoft exchange server address book was unable to log onto exchange". If I then try to log into outlook I get "the microsoft exchange server address book was unable to log onto exchange"". The email account works fine on another machine that is vista and outlook 2007. If it's any help Lync still works but I have to manually add proxy settings to get it to work, but it has always been like that. One strange thing is that when I try to log into the old outlook profile (that was working before the issue), the login box shows "connect to outlook.office365.com, connecting to firstname.lastname@example.org" (I have replaced my real email address with email@example.com for privacy) , whereas on the vista pc that works it shows " "connect to outlook.office365.com, welcome back to outlook.office365.com".
This is only happening on one PC. The PC in other respects has no issues, can still access the internet, and can access office 365 through the portal with no problems.
There is another PC that is also XP and office 2007 and can connect fine with another user's mailbox (am unable to try with my mailbox).