When trying to create a User having dashes and numbers in their email address domain you get an error message.
Steps to reproduce:
- **Create a new User in the Control Panel using Control Panel --> Users --> Users and Organizations --> Add-Button
- Type in a valid Screen Name, First Name and Last Name
- Type in an email address containing dashes and numbers, e.g. "firstname.lastname@example.org"
- Press the Save button
- The user should be saved
- An error message "Please enter a valid email address" is shown
According to the RFC 5322 the email address "email@example.com" is a valid email address.