What server are you using? Yahoo ? What comes after the @ in your email address?

re :Please verify that your email address is correct in your account settings

right click on mail account name in Folder Pane and select 'Settings' select 'Server Settings' Email address = full email address you can completely remove to ensure no hidden blank spaces and then retype the full email address. Make sure you do not add a full stop at the end nor add a space. click on OK

Thank you. Somehow the email address was altered to the website address. I don't do this so Thunderbird must have. Might be a bug. Thanks Toad-Hall for your help.