Thunderbird has to send via the smtp protocol, so just because it works from the webmail account does not mean it's working.

That error message means Virgin server does not like whatever you have set up to use for sending from that account.

Please post the following information so we understand the current settings. In Thunderbird Help > Troubleshooting Information Scroll down to 'Mail and News accounts' Copy all the data in that area and then paste it into a reply box in this forum question.

It will tell us what server settings are currently being used and whether you have more than one account.

Bill,

Please add more details.

Virgin help is only interested if you have an issue with their webmail account and by the sounds of it they have little knowledge etc on third party email clients using pop, imap and smtp protocols. They also do not seem to understand what their own error message means otherwise they would have explained the issue and how to fix it.

Authentification error (VM401) is a very specific error message from Virgin Media and it means Virgin is refusing you access via smtp because you are not using the correct authentication settings, but we cannot help/advise you if you do not communicate with required information. You may use Virgin but that does not necessarilly mean you are using a virgin email address nor does it mean you are using the most recent Authentication requirements set up by Virgin. I cannot waste time guessing, so please respond or let us know if you have already fixed the problem.

Sorry my pc froze when ms screwed the other week. It looks like it has also overheated. It is in for repair but looks like a new machine. Will instal third and try. Please keep my request live and thanks for your patience. Bill

Just installed latest version of thunderbird on my new laptop. Can now send messages. Nothing changed on Virgin Media. Still say the issue was with TB. Thanks for your patience. Bill