As you are named as the bill payer on your fathers account you have rights to access his mailbox which is technically yours. If you have his adsl username and password login using the webmail client at
http://webmail.zen.co.uk and delete the email from there. If you don't have these details, speak to our support team who will be able to provide the login details to you, be quick though!
David NelsonTeam Leader
Business Support Unit
Zen Internet