Thunderbird cannot setup Outlook mailbox after upgrade to Windows 11 clearing passwords from the credentials caches in TB and windows makes no difference. Changing the password for the Outlook mail account and verifying it makes no difference. No problem with 14 Gmail account accounts Outlook and Thunderbird are a buggy pair. They will waste hours of your time. Experts will tell you that you’re an idiot and it’s really simple. But they can’t describe how to simply start from scratch and add an Outlook account. They just assume it works naturally for everybody because it worked for them. Maybe it does work 60% of the time. Good luck plan to spend a frustrating evening and then think about something other than Microsoft and Mozilla.