Thunderbird failing to connect to IMAP mail.btinternet.com

[FloFosterJenkins]

Mail was ok until Nov 16. No mail received since then. Settings show mail.btinternet but error message refers to yahoo server as in pic attached.

Another account had exactly the same problem - solved by deleting account and reinstalling it, a PITA.

Is this a Thunderbird authentication issue ( I think they had a big upgrade recently, and now seem to be on an unfamiliar to me "OAuth2" authentication setting, not "Password") or a BT mail issue?

[FloFosterJenkins]

god knows what happened to that image... can't edit it. Software's not what it used to be

[imjolly]

looks like using the old Yahoo servers and not the newer btinternet server

i use Thunderbird and can send and receive email on my btinternet email address

[licquorice]

@FloFosterJenkins  You have probably been migrated to the BTMail system, the correct settings are here 

[FloFosterJenkins]

Thank you both for the replies.

My Thunderbird email settings (I double-checked) are mail.btinternet.com, so that's right.

I just checked Thunderbird settings on another desktop, same account; the Authentication method is "Normal password", whereas on the problem desktop the Authentication method is "OAuth2" . I've never heard of that, and certainly didn't enter it manually, so will try changing that to "Normal password".  Maybe it's always been there, as these days when setting up a mail account mail clients configure themselves automatically once they recognise the server, and one doesn't need to look at the server settings if it's all working smoothly; but maybe the Thunderbird upgrade "upgraded" the Authentication method from Normal password to OAuth2.

What's odd too is that the popup error message that I attached refers to the yahoo server when the account is plainly configured to the correct btinternet server.

[licquorice]

Authentication should definitely be normal password.

If you are still on the BTYahoo mail system, the correct server setting is still mail.btinternet.com but it will re-direct to the Yahoo servers which might explain the error message. 

[FloFosterJenkins]

Thanks again for replies.

I checked the reinstalled BT account on Thunderbird that is now working - sure enough it had set by default to "Normal password". Changed the defective Thunderbird account setting from "OAuth2" to "Normal password".

That did it. I assume that one of the recent Thunderbird updates was to blame - reconfiguring Authentication to a setting that is incompatible with current BT/Yahoo server settings. I don't know if the mods here can flag this up in a more prominent place; it could be a pretty widespread issue, and save folk an awful lot of time and frustration.

[imjolly]

@FloFosterJenkins 

not sure how widespread as you are only one so far to post  I use thunderbird and didn't have any problems with btinternet email

[licquorice]

I don't use Thunderbird regularly, but have a test account set up to replicate forum problems and haven't had any problems with upgrades changing authentication.

[FloFosterJenkins]

The rogue account stopped receiving emails on Nov 16, and I assume that is when the password Authentication switched to 0Auth2.  I hadn't gone near Settings, so goodness knows how the Authentication changed. Several other Thunderbird accounts are all still set to "Normal Password", and have continued to function normally, as far as I can tell. I think I'll never understand this little mystery. Here's something from Thunderbird about OAuth2 that might be of interest:

https://support.mozilla.org/en-US/kb/thunderbird-and-yahoo