My Thunderbird Office365 email quit sending. It happened about 2 weeks after I installed Ubuntu 20.04 on my system. I think it was coincident with an update of the system. My other emails work fine. It tells me the auth failed because "SmtpClientAuthentication is disabled for the Tenant." Thunderbird has a limited number of SMTP authentication methods, and I tried them all. I went to the page the error recommends, and it is for exchange servers. I have microsoft365 from GoDaddy. Any help would be appreciated. -Dave Thunderbird 68.10.0 (64-bit) Here is most of the log, minus most of the startup handshake. [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 21 [(null) 9682: Main Thread]: D/SMTP SMTP auth: server caps 0x30134, pref 0x300, failed 0x0, avail caps 0x100 [(null) 9682: Main Thread]: D/SMTP (GSSAPI = 0x800, CRAM = 0x2000, NTLM = 0x4000, MSN = 0x8000, PLAIN = 0x200, LOGIN = 0x100, EXTERNAL = 0x400) [(null) 9682: Main Thread]: D/SMTP trying auth method 0x100 [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 15 [(null) 9682: Main Thread]: D/SMTP SMTP: MSN or LOGIN auth, step 0 [(null) 9682: Main Thread]: I/SMTP SMTP Send: AUTH LOGIN [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 0 [(null) 9682: Main Thread]: I/SMTP SMTP Response: 334 VXNlcm5hbWU6 [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 13 [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 16 [(null) 9682: Main Thread]: D/SMTP SMTP AuthLoginStep1() for [email protected]@smtp.office365.com [(null) 9682: Main Thread]: D/SMTP LOGIN auth [(null) 9682: Main Thread]: I/SMTP Logging suppressed for this command (it probably contained authentication information) [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 0 [(null) 9682: Main Thread]: I/SMTP SMTP Response: 334 UGFzc3dvcmQ6 [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 18 [(null) 9682: Main Thread]: D/SMTP SMTP Login response, code 334 [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 17 [(null) 9682: Main Thread]: D/SMTP SMTP AuthLoginStep2 [(null) 9682: Main Thread]: D/SMTP LOGIN auth, step 2 [(null) 9682: Main Thread]: I/SMTP Logging suppressed for this command (it probably contained authentication information) [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 0 [(null) 9682: Main Thread]: I/SMTP SMTP Response: 535 5.7.139 Authentication unsuccessful, SmtpClientAuthentication is disabled for the Tenant. Visit aka.ms/smtp_auth_disabled for more info. [SJ0PR13CA0187.namprd13.prod.outlook.com] [(null) 9682: Main Thread]: I/SMTP SMTP entering state: 18 [(null) 9682: Main Thread]: D/SMTP SMTP Login response, code 535 [(null) 9682: Main Thread]: D/SMTP marking auth method 0x100 failed [(null) 9682: Main Thread]: D/SMTP SMTP auth: server caps 0x30134, pref 0x300, failed 0x100, avail caps 0x0 [(null) 9682: Main Thread]: D/SMTP (GSSAPI = 0x800, CRAM = 0x2000, NTLM = 0x4000, MSN = 0x8000, PLAIN = 0x200, LOGIN = 0x100, EXTERNAL = 0x400) [(null) 9682: Main Thread]: E/SMTP no auth method remaining [(null) 9682: Main Thread]: W/SMTP SMTP: ask user what to do (after login failed): new password, retry or cancel [(null) 9682: Main Thread]: W/SMTP cancel button pressed [(null) 9682: Main Thread]: I/SMTP SMTP Send: QUIT