I can receive email fine but when trying to send any email always get the above msg and takes a long time to send. Sometimes I try number of times to re-enter the password, and finally it send. Occasionally it works after three or four attempts, with no clear reason. Updated other computer to TB 38.7.0 and same problem has appeared. Here are Server Settings for that Yahoo mail plus account. User Name has the full email address entered : User Name: tomsalmon@yahoo.com Server name: imap.mail.yahoo.com Port: 993 Connection security: SSL/TLS Authentication method: Normal password Outgoing server: smtp.mail.yahoo.com Port: 587 Username: tomsalmon@yahoo.com Authentication method: Normal password Connection security: STARTTLS Have, of course, just tried to test this again many times by sending emails to myself. This computer runs Windows 7 with Kaspersky (with Mail Anti-Virus disabled). Only one email account on TB. In passwords section from the Options menu / security I have tried deleting my smtp password and re-entering it a number of times. Have also tried to ping Yahoo smtp from command line to check for packet loss - none shown. Have tried setting up new email account on TB, with same details to verify login. It comes out positive at least at verification stage. Tried switching from STARTTLS back to SSL/TLS with smtp port 465. No change, same problem Strange thing is I have the same Yahoo account configured on other computer Win8.1 and it also ran Kaspersky but with TB 38.6.0 and it had no problems. It automatically updated itself today and now the exact same behaviour is being replicated on that other computer with TB 38.7.0 The difference I thought initially on inspection between the computers originally might have been that the WIn8.1 machine with 38.6.0 carried 2 identical passwords in the Options / Security / passwords menu (which have been in place for a long time with no change, so no problems with login for a long time). One: imap://imap.mail.yahoo.com The other: smtp://smtp.mail.yahoo.com The WIn7 TB 38.7.0 computer has only one password there for imap://imap.mail.yahoo.com in the security options menu but it doesn't have one for smtp://smtp.mail.yahoo.com But in fact this makes no difference. It was the update to TB 38.7.0 that has caused the SMTP login problem with Yahoo on both computers. I have also tried 'Restart with add-ons disabled' and unfortunately the problem is still there. It asks me for the password, I enter and then it takes a long time with the green bar and says 'Connected to smtp.mail.yahoo.com but then 'Login to server smtp.mail.yahoo.com failed' options are: retry, enter new password or cancel. Then I try to enter new password and also click remember this password. Same behaviour again. If I click 'retry' it will again attempt and result with same 'Login to server smtp.mail.yahoo.com failed' The fourth time I try to re-enter the password again it does send the email. This can be replicated in SAFE MODE but also can be not seemingly not in safe mode, it just takes a number of attempts for the authentication to go through seemingly by clicking 'retry' or 'enter new password' in safe mode but it also seems random to be honest. Tried saving the msg into drafts and sending, same problem. I have attached what is in the TB error console but that does not seem to relate. See picture.