Thanks for getting back to me Eleanor,
You do need to have an active broadband account in order to use the email service, this is usually removed 90 after leaving us.
Sometimes if the email address is in constant use it can be missed, we go through and do a clean up and as such, any email address no longer associated with an active account are deleted and removed.
I've sent you a private message to get a few more details from you (purple envelope, top right hand corner) to see if I can help, but I do need to set the expectation I may not be able to help.
Alex