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401 error on attempting to connect to outlook.com calendar

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  • Last reply by srboardman

srboardman
srboardman
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Running Thunderbird 115.8.0 (64 bit) on Windows 11.

Until recently all was working well accessing an outlook.com calendar (on server outlook.office365.com) using tb-sync and Provider for Exchange ActiveSync (latest versions).

Now I get the following error: "Could not authenticate, check username and password (HTTP Error 401)." (Meanwhile email is working fine with the same credentials).

I then tried using the new Thunderbird non-add-on exchange calendar integration, with identical results.

I then deleted all the cached outlook passwords (settings -> Privacy and Security -> Passwords -> Saved Passwords) and tried again, with identical results.

Interestingly, after deleting the passwords, closing and reopening Thunderbird, it successfully downloaded new emails from outlook.com (in spite of supposedly not having the passwords).

Help please.

Running Thunderbird 115.8.0 (64 bit) on Windows 11. Until recently all was working well accessing an outlook.com calendar (on server outlook.office365.com) using tb-sync and Provider for Exchange ActiveSync (latest versions). Now I get the following error: "Could not authenticate, check username and password (HTTP Error 401)." (Meanwhile email is working fine with the same credentials). I then tried using the new Thunderbird non-add-on exchange calendar integration, with identical results. I then deleted all the cached outlook passwords (settings -> Privacy and Security -> Passwords -> Saved Passwords) and tried again, with identical results. Interestingly, after deleting the passwords, closing and reopening Thunderbird, it successfully downloaded new emails from outlook.com (in spite of supposedly not having the passwords). Help please.

All Replies (1)

srboardman
srboardman Question owner
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Additional info. I also tried turning on Outlook two factor authentication and using an app password, and that didn't work either. (I then disabled two factor authentication and tried again with the original password and that still didn't work.)