OK. This is about TB then, not Firefox. That you refer to both ( they're two totally different programmes and only one does the email) sort of makes me wonder what level of skills you have. But I assume you set up the email in the first place ( and knew to use TB and not just web based mail or Outlook) so do have the know how to do that. Have you looked at your account settings and checked that they are all present and correct? If my assumption is wrong and you don't know how to do this there are plenty of helpful guides online. Is your email coming from an email provider or are you using TB to access a web based email service through the pop or imap?