Who has told you that it has been compromised and therefore must be deleted? Ordinarily just changing the password is sufficient to regain control of an email account. I receive messages that say they are from me, but on inspection it is clear that they were sent by someone else but with my email address inserted in such a way as to make it look like it was from me. Usually there is someone else's email address in the background and invariably an IP address that indicates that it was actually sent from some distant part of the world. At face value you might think my account had been "hacked" but in practice all that is happening is that my email address, a mere string of letters, is being misappropriated and abused. Your email account is set up for you by an email provider. You need to work with them to cancel an account. Thunderbird is just a tool for accessing an email account. It doesn't have the capability to create or destroy an email account. If you don't know who your email provider is, tell us the part of your email address after the '@'.