Is there anything else you may be able to tell about your problem?

https://support.mozilla.org/en-US/kb/ask-tb#w_how-to-ask-your-question

Whose server is it?

You apparently think this is something to do with Thunderbird. But Thunderbird is just an email program that runs on your computer. You need to check with your mail provider who operates the server that Thunderbird talks to in order to get your incoming messages.

The part of your email address after the '@' indicates who provides your email service.

Mozilla don't run any email servers for Thunderbird users.