Assuming Yahoo, as you didn't state which provider. This is a Yahoo problem. This is the usual fix: First, generate an app PW - see https://help.yahoo.com/kb/SLN15241.html. Then go to TB menu > Settings > Privacy & Security > Passwords: - click the 'Saved Passwords' button and edit the Yahoo entry to add your new app PW - if there is no Yahoo entry, it should be created when you next log in successfully Next, 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 After that's done, click your Inbox. If you need to enter a PW, enter the app PW you just created.