Hi there Jacky,
First off i would advise you to change your password straight away.
Chances are that some one has set up a mail clinet and not ticked the "keep a copy of messages on the server" box.
This means that when the mail clinet (Outlook, Livemail, Mac mail etc) synced with the webmail all the messages on the server were downloaded and deleted from the webmail.
There are a few other things that it could be (exchange account set up and something happening to the PC etc)
Either way changing the password will stop this from happening again.
Second, in regards to recovering the mail.
If you go into the webmail then go to deleted items then right click on this you will see recover deleted items.
Click that and you will see a new window, select the email that you want to recover and then move this back to the approriate folder.
If the email is not in the recovery section then i am afraid that it is gone for good and that there would be no way to recover this from the BT webmail.
That being said if you have had a copy of this on your PC and this has disappeared most PC shops will either have someone who can recover data or will have a contact for a specialist company who can do this for them.
I hope this helps
