First, generate an app PW - see https://help.yahoo.com/kb/SLN15241.html.

Then go to TB menu > Account Settings > Server Settings and set the following:

- Server Name: export.imap.mail.yahoo.com - Port: 993 - Connection Security: SSL/TLS - Authentication method: Normal password

On the left column, scroll down and click 'Outgoing Server' and edit the Yahoo entry:

- Server Name: smtp.mail.yahoo.com - Port: 465 or 587 - Connection Security: SSL/TLS - Authentication method: Normal password

Finally, go to TB menu > Settings > Privacy & Security > Passwords

- click the 'Saved Passwords' button and edit the Yahoo entry to add your new app PW

After that's done, try logging in.

BTW, this fix is mentioned in the related [bug](https://bugzilla.mozilla.org/show_bug.cgi?id=1997062).

Hi Ed, It all worked until Thunderbird couldn't recognise the host server. But 'saved passwords' had no entries and one for Yahoo couldn't be written in. But I can sign in to Mozilla using Gmail.

Best wishes, Kitty

Hi Ed,

I managed to use my (hated but useful) Gmail account to sign in and Thunderbird is up and running again. I hope I can get used to the horrible - clunky - layout! I suppose one must suffer for ones principles - though the Gmail and Outlook layouts are just as bad.

Many thanks for your help. Best wishes, Kitty

Hi Ed, It all worked until Thunderbird couldn't recognise the host server. But 'saved passwords' had no entries and one for Yahoo couldn't be written in. But I can sign in to Mozilla using Gmail. Best wishes, Kitty

Try using imap.mail.yahoo.com instead.