This is almost a blog
I’ve recently (late December 2022/early January 2023) been getting an error message from my Thunderbird client, while attempting to access my employer’s Office 365 email account.
User is authenticated but not connected.
The solution is to disable IPv6. I’m not sure exactly what has changed, but you solve this by opening Settings, then going to > General > Config Editor… button > Search for ipv6 > Change network.dns.disableIPv6 to true.
Post written by Lance Bachmeier