Your email provider is not Thunderbird, but the organization from which you have the account itself. There appears to be a problem between those senders and your account server receiving the messages.

Did not understand. My email provider IS thunderbird and has been so for many years.

                      B Traylor

Let me explain: your email provider is identified by whatever is to the right of the @ in your email address, such as @gmail.com, @outlook.com, etc. If you are unsure, please post that part of your email address and we will attempt to advise on who your email provider is. Thank you.