Current OS is Linux Mint 21.3 Cinnamon, and until October 2024 I've successfully used Thunderbird for years without issue. I can reliably receive and view messages, but after carefully checking all IMAP & STMP server settings, remain unable to send any outgoing messages for past couple of weeks. I do not own a mobile phone to be able to receive temporary codes or do any type of two-step authentication. When attempting to send messages, here are the repeated error messages leading to endless loop that eventually times out: Login to account "Microsoft" failed Login to server smtp.office365.com with username xxxx@outlook.com failed. Send Message Error 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. Send Message Error Sending of the message failed. Unable to authenticate to Outgoing server (SMTP) smtp.office365.com. Please check the password and verify the 'Authentication method' in 'Account Settings | Outgoing server (SMTP)'. Current Server Settings: IMAP Mail Server outlook.office365.com Port 993 xxxx@outlook.com SSL/TLS OAuth2 Default Outgoing Server (Microsoft) smtp.office365.com Port 587 xxxx@outlook.com STARTTLS OAuth2 No so-called 'solutions' that are currently online have any effect. What do you suggest? Thanks!