When trying to sign up for a new Zendesk account, I receive an error that states Please enter a valid email address.
This error often occurs when trying to enter an address with a prefix like support@ or help@, which are not allowed. The email address you should be entering at this stage is an address that is unique to you, as this will be the address that you use to log into your account.
After you create your account, you will be able to select a support address that customers can use to contact your support team.
For more information on creating a new account, see this article: How do I create a Support trial account?