Hello,

Outlook may have disabled normal password authentication. Try changing your authentication method to OAuth2 and log in through Microsoft's web portal.

Tell us if this worked, we'd love to hear it!

Amanda --

Very much appreciate your interest/effort. Sorry, forgot to mention in my original posting that I found that tidbit about OAuth2 in some postings from a couple of years ago, and though it still didn't make sense that such a major change would only have been implemented two years later and without warning, I tried it anyway. After making that adjustment in my account server settings in T-Bird, when I next tried to login to the account, a Microsoft window popped up showing my e-mail address and asking me to enter the password, and there was a bit of delay after I entered it, but Thunderbird eventually popped up a message that authentication failed. Tried going back to Normal password, and of course that also failed again, so I then tried switching back to OAuth2 and saw the same sequence of events again. And yet, again, I'm still accessing the account just fine via Outlook Web and Outlook Android, so I know the account itself is OK and the access codes remain the same; it's just the access *route* (via T-bird) that suddenly broke at some point on Sun Apr 24. Makes no sense (until, of course, the "right answer" becomes apparent  :-) ).

-- LBA

Hmmm, this is getting weirder and weirder. Given that on Apr 24 T-bird somehow lost the ability to connect in to regular IMAP and SMTP services on office365.com, I tried today to set up a separate account via Exquilla to connect T-bird to my mailbox on my office365.com server. I've used Exquilla in the past to connect to the Exchange server at serverdata.net (which used to provide my office's e-mail and other cloud services), but since my office switched from serverdata.net to office365.com last December, I had just been using standard IMAP/SMTP to connect to the mail server at office365.com. So today I tried going through Exquilla's account set-up process. I entered my e-mail address and password, didn't change the already-selected "Login with email address (recommended)" option, and hit Next. On the next screen, I didn't change the already-selected Autodiscover option, and clicked the "do auto discover" button. There were some messages that flashed by very quickly in the message line right below that button, then a brief pause, and then an error message popped up saying "Validation request responded after maximum elapsed time exceeded. An Autodiscover site was found, but we could not find a usable entry. This is probably because your server does not support Exchange Web Services (EWS). If your server does not support EWS, then ExQuilla will not work for you. If you believe this to be in error, try manually entering the EWS URL." So at that point (still on the same ExQuilla config pane), I switched the Autodiscover option to Manual, I left the default Microsoft Exchange EWS URL entry unchanged (https://outlook.office365.com/EWS/Exchange.asmx), and I clicked on the Test EWS URL button....which appeared to do absolutely nothing. I tried clicking on it a few more times, and nothing ever seemed to happen -- and the grayed-out Next button for moving on to the next pane after establishing a successful connection with the server never became active.

So T-bird no longer can connect to office365.com via IMAP/SMTP, and it also cannot connect to office365.com via EWS. Can anybody think of any other way to get T-bird to connect to office365.com?

Meanwhile, I'm going to speak with my office's tech support folks tomorrow and see if they can "open a trouble ticket," or something like that, with Microsoft about this issue, as it's my impression that this is increasingly looking like something Microsoft did on Sun Apr 24 to break all of the access routes to office365.com other than via Outlook.

-- Larry Afrin

Just wanted to close the loop on this thread:

I sure hope I'm not jinxing things by posting this, but...

Because I don't have better things to do at 11:30pm on a Tuesday night after a 16-hour workday, I tried again just now to get in to my office365.com e-mail account via Thunderbird, and with no change in the configuration I've long been using (i.e., still with "Normal password" security, not OAUTH2), it worked!!!! Not just IMAP, but SMTP, too.

Halleuluiah!!!

Obviously, somebody at Microsoft finally realized what they had done and the trouble it caused and managed to reverse it.

Hurray!

-- Larry Afrin