Hi Roy Try searching for 'Client host rejected: Access denied' in this Thunderbird support site. You will find several people who had the same error message and answers that worked for them. It seems related to email providers using another email provider's SMTP servers, or with SMTP settings in Thunderbird using the wrong SMTP server address. If you can confirm the correct current SMTP settings for your email provider (often can be found online), then compare with the SMTP setting in Thunderbird, you may be able to correct the problem. It may also have to do with the settings that control your password and security (2 factor authentication) for connecting to your provider's email servers.

Thanks for your reply. I tried your suggestions, none worked. I thought it odd that an other mail app worked but thunderbird didn't. My solution was to purchase a new computer, all is well now. Roy