hello, you're posting in the firefox support forum - firefox is a browser and doesn't handle your emails. in case you're using thunderbird as a mail client and have a question about it please say so, then we will move your question into the thunderbird queue. if you're accessing your mails through webmail, contact your email-provider in order to help you further...

Problems with email and how to find help

Thank you for your reply which, though it has not solved my problem, it has enlightened me and I shall have to look elsewhere!