For a couple of weeks now Thunderbird has a problem with Yahoo mail. The "User Identification Request" window keeps popping up with the message: "This site has requested that you identify yourself with a certificate: imap.mail.yahoo.com: 993; Organization: Oath Inc; Issued under: DigiCert Inc; Choose a certificate to present as identification:" It seems to be fetching Yahoo mail nonetheless if I 1) click Cancel or 2) choose a certificate. It keeps popping up even if I choose a certificate and tick "Remember this decision". It must be a change on Yahoo's side because I haven't changed server settings for Yahoo mail for months. It is annoying because it is a safety concern (why would a site like mail server keep asking for my certificate) and it is a tiresome bother (it keeps popping up every time I am working with Thunderbird).