I'm really sorry for you current email issues, I'll do what I can to help
How are you sending mail, via a client (such as Outlook, Thunderbird etc) or webmail? If you use a client please try to send from webmail and let us know if it works for you.
What error message is returned when you fail to send? Please copy/paste the returned error (though edit out any personal information first, such as your email address) and post it on here. I shall send you a PM (purple envelope icon, top right of page) in a moment requesting some information relating to the email address. I'll check a few things on our systems as soon as I get your reply