Firefox doesn't do email, it's strictly a web browser.

If you are using Firefox to access your mail, you are using "web-mail". You need to seek support from your service provider or a forum for that service.

If your problem is with Mozilla Thunderbird, please Tag this thread as being for Thunderbird in the right-hand column of this page. This question currently is in the Firefox queue for answers.

On most e-mail providers, only the junk folder is cleaned out now and then.