I've used Thunderbird for a zillion years and I've had the same Yahoo email address for 21 years. Over the past year, Yahoo forced its users who use third-party email clients to switch to IMAP access instead of POP access. I've had frequent problems with this and now it is a daily occurrence. I have Thunderbird set to check for new mail every 10 minutes. Yesterday, for example, that function failed for most of the day and returned the error message: "Login to server imap.mail.yahoo.com failed." It started working again sometime last night (I left my computer on) because this morning all of my new emails from yesterday were now displayed in Thunderbird. But mid-morning today it started failing again. I've tried searching various forums and a lot of people are having problems with Yahoo email. One theory is that Yahoo is doing it on purpose to try to force its users to use their webmail client! When this happens, I cannot SEND email, using Thunderbird, through my Yahoo account. I have to go to the webmail client to send email. My Thunderbird settings are set as follows (and these settings do work when Yahoo is talking to Thunderbird): Incoming server name: imap.mail.yahoo.com Port: 993 Connection security: SSL/TLS Authentication method: Normal password Outgoing server name: smtp.mail.yahoo.com Port: 465 Authentication method: Normal password Connection security: SSL/TLS Does anyone use Thunderbird with Yahoo mail, and do you have any suggestions for me?