I don't believe you can change the email address, but there's nothing stopping you from creating a new account. You could then unlink and relink the Slingboxes to the new account. (https://slingaccounts.slingmedia.com/Accounting/Web/Account.html)
Thank you for participating in the Slingbox Answers Forum!
This link will allow you to get all the information you need to know about how to change the Sling Account e-mail address.
The Slingbox Answers Forum Moderation Team.