My mailbox always ir empty
Most believable, that you have retrieved all your messages useing POP3 program, for example,Outlook, TheBat etc.
Unfortunately, it is not possible to return the deleted messages. You should check your Outlook or other POP3 client-program.
In case the message forwarding is set to other mailbox, all the messages should stay inside your mailbox.
Also possible, that someone got to known your password and has deleted all your messages.
If you were unable to find answer for your question, please write to firstname.lastname@example.org