Is the authentication set to OAuth2? Here is a working setup.

I tried doing what sfhowes said and got a message saying the server does not accept the OAuth2 authentification.

Incidentally, I'm in UK, if that makes any difference.

I had to remove and re-add all hotmail accounts. AND YET, I get errors connecting. Also errors connecting to AOL. The last update is SUPERNOVA indeed!!! and that's already 115.6.1! I bet the first of this SUPER nova was just awful. And than Thunderbird support asks me why would I want to stick to non-supported all version! the answer is SUPER simple - because it WORKS!

Even weirder, It will SEND messages even though it keeps saying: Login to server imap-mail.outlook.com with username ___________@hotmail.com failed and won't let me see the messages is my Inbox or Junk folders.

Or, for that matter my Sent folder (I know it sent the message because I sent it to my aol address.)

Even weirder, It will SEND messages even though it keeps saying: Login to server imap-mail.outlook.com with username ___________@hotmail.com failed and won't let me see the messages is my Inbox or Junk folders.

Did you see the settings in the link in my first reply? The incoming IMAP server is outlook.office365.com (the outgoing is smtp.office365.com).

sfhowes:

Originally both my and my husband's hotmails were set to the office 365 server names. 1.First I tried only changing the authorization from normal password to the OAuth2 like you suggested and got the message that the server didn't accept that authorization so I put it back to normal password. 2. I tried removing and re-adding only my account from and to my Thunderbird like the other person's answer mentioned, using the IMAP incoming and outgoing server names given in the "Thunderbird and Hotmail" thread on this site'which are imap-mail.outlook.com and smtp-mail.outlook.com. After about 15 minutes it worked (for about 10 minutes) and then it stopped working. Now, 3 hours later it's working again, at least temporarily. And strangely, the server names have changed in my husband's account too even though I didn't change them!

        In addition another intermittent peculiarity is that for the last several months none of the 4 accounts i have on Thunderbird will send a message the first time I try to send it, then after 2 or 3 tries it will send it.  There must be some sort of intermittent bug in Thunderbird.

As long as you have the settings linked in my first reply, there should be no issues with hotmail/outlook.com/live accounts. But if you have a non-MS antivirus such as AVG or Avast etc. that is scanning outgoing mail, that is a potential cause of sending errors (also, if a VPN is used). Note also that since these MS accounts copy sent messages automatically to Sent, 'Place a copy in' in the Copies & Folders section of Account Settings should be unchecked to avoid additional errors.