Assuming you are broadband customers (emails are only provided to broadband customers), then try this first. Log in to your billing account and see if the email address is linked to your account. It would show on the my profile tab (scroll down to my services), or on the manage accounts tab (those are any secondary addresses you control).
If the address shows - then bingo - you have control and can reset the password.
If not, perhaps it is an orphan address from a previous account with VM? Then you would have to wait for assistance from the Forum Team (VM employees) who can check the records and see what can be done. But don't get too hopeful.