I had a yahoo account configured on my laptop with Thunderbird and it worked flawlessly. I need to change to a gmail account, so I edited the account settings, changed the email addresses, changed the IMAP & SMTP settings etc. to the new gmail settings. I am able to receive mail just fine, but am unable to send mail. I get a yahoo prompt to sign in each time I try to send mail (attached). I close that prompt and then receive a message Sending of the message failed. Unable to authenticate server (SMTP) smtp.gmail.com. Please check the password and verify in Account Settings. I have removed saved passwords and verified all settings. Could there still be something hanging on from the old yahoo account? At this point I have uninstalled TB, reinstalled, removed all accounts, recreated them. Nothing seems to allow me to authenticate to the SMTP server. I am using Port 465, server name smtp.gmail.com, Authentication method OAuth2 and connection is SSL/TLS. Any other ideas? Thank you! Lisa