What happens if you try this: set the incoming IMAP server to imap.mail.yahoo.com, port 993, SSL/TLS, OAuth2 authentication, User Name = username@yahoo.fr; outgoing SMTP server to smtp.mail.yahoo.com, 465, SSL/TLS, OAuth2 authentication, User Name = username@yahoo.fr. Restart TB, enter the account (not app) password in the OAuth window to allow access. Cookies must be accepted in Settings/Privacy & Security.

@sfhowes No I have already tried that. The OAuth window opens, it just leads to yahoo.com and it says there the account does not exist.

If it doesn't work with OAuth2 + account password, or with normal password authentication + app password, I'm not sure why. Perhaps try the suggestion here to use export.imap.mail.yahoo.com for the incoming, with normal password authentication + app password, or possibly OAuth2 authentication + account password.

The problem is that yahoo's app passwords no longer work for this for some reason.. The only way is OAuth2..

But Thunderbird is sending to yahoo.com and not yahoo.fr

Seems like a program issue to me. Can this be reported to the dev team?

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