Hello, I have two microsoft email addresses linked to Thunderbird, one @hotmail.com and one @outlook.com. I have been using Thunderbird with them both fine for some time. Recently, the outlook.com account has stopped sending emails via Thunderbird. As far as I can tell, this was out of nowhere, and I hadn't changed any settings. It still receives emails. Both accounts use the same SMTP information, and the hotmail.com continues to work with those details. I have tried changing the settings and even deleting and readding the account but it hasn't fixed it. I have also checked the outlook account is still IMAP and POP enabled and it is. When I do try and send an email, I am told: "Login to server smtp.office365.com with username bufflehead_mike@outlook.com failed. with options to Retry, Enter New Password (which loads a new window briefly but then disappears) and Cancel." When I cancel, I get this message: "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.office365.com timed out. Try again." My server settings, on both accounts, are: smtp.office365.com Port 587 STARTTLS OAuth2 And the user name matches the email. Does anyone know what I might be doing wrong, and how I could fix it? Thank you!