Office 365 Says Password Is Invalid After 2 Days

[Mystic Mungis]

My mum works at a small company and if they ever have any technical problems I always go in to help out, last week I got a call and the girl said that she couldn't access her E-mail via Outlook and the password showed up as being incorrect via the web interface. After a couple of tries I put in the old password which worked, I thought at first I had been mistaken and hadn't changed hers along with everyone else (they have a BT Business account and all of the E-mail used to be through BT but recently it got switched over to Office 365 which required new passwords for everyone) so tried it in Outlook and it was still returning an authorization error.

At this point i just changed the password from the web interface, tried it in Outlook and it worked so that was fine, then on Friday the same thing happened again so I called up BT and they just kept telling me it was my settings, eventually after reading out every setting they confirmed that it was set up correctly and admitted they had no idea what the problem was so were going to contact Microsoft and get back to us then I changed the password again and everything worked fine. Got another call this morning saying that it had happened yet again but by this point she knows how to fix it herself and still no word from either BT or Microsoft so does anyone here have any idea what the problem could be? I'm 99% sure the problem is at their end as there are 9 other accounts and they all work fine with the same settings and software.

Ohh also every time it seems to reset itself back to the original password that we used while it was still BT hosting the mail which makes me think it may have been an error left from when they switched us over.