Check your username.

Right click on mail account in Folder pane and select 'Settings' At bottom of left Pane, click on 'Outgoing Server (SMTP)'

This will show a list of all your smtp outgoing servers. select the one you use for the account. UserName: it is usually your full email address, but some only use the part before the @ symbol. Check the spelling. Make sure there is no full stop at the end.

Use 'EDit' button to faciliate editing. click on all 'OK's

Sorry Todd, Thanks for helping I still get error message when I click on IN box Regards Tom

syntax error is the clue, my internet mauinet says these two words means thunderbird is the problem?

Has it ever worked? If so, what changed at the time it stopped working? Or is this a new account, or the first time you have used Thunderbird?

Yes until 3 days ago nothing had changed that I know of. Have used for last three years Thanks Tom

When you get the syntax error what number is shown eg: 500 or 501 etc ?

Do you use an Anti-Virus product to scan outgoing emails ? If yes, access the AV product and switch off scanning outgoing mail.