Turned on my computer this morning to find all emails all gone and it is asking me to set up an account again. If i set up again will my saved emails be restored?
Who held your account previously. They should have copies somewhere. Contact them and ask.
Ok, this is a silly question -- are you sure that you are logged in to YOUR account, and not a separate system administrator account?
(Been There Done That Got The T-Shirt)
If you have Time machine enabled, set your page to Mail > go into Time Machine > then scroll back. You should reach a time when the mailboxes existed and you can then click 'restore'. Then cross your fingers.
Retrieving data ...