I use Thunderbird to collect business email from BT. Business email are addreses that end @btconnect.com. Suddenly one of my email addresses failed to authenticate. I rang BT to find out why. Apparently BT business email uses Exchange servers. I don't know why they do that, I would have thought some sort of Linux server would be better and more efficient. Microsoft have decided that Exchange will no longer support POP3 where passwords are sent in the clear. It's too vulnerable to hacking.
https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/deprecation-of-basi...
So if you have business email, your only alternative is to connect to BT mail using webmail! So they are gradually turning off authetication by pop3 clients. I have lost two addresses so far.
Exchangeserver will support client connections that use oauth2 authentication, but for some reason BT exchangeservers won't accept it. I've sset it up in Thunderbird and it doesn't work.
BTW google also supports oauth 2 (now) and I've transferred my gmail to that smoothly.
I can't understand why nobody else seems to be worried about this
