If you try to create a new user in Sitecore with an email address as account name you will be met with a validation error:
“user name is not valid in the selected domain.”
But do not worry, it’s not the underlying security framework that disallows email as username, it’s just a default validation of user names in the user manager dialog box.
The default validation is based on this regular expression: ^\w[\w\s]*$
You can change the regular expression using the AccountNameValidation setting. Add the following to your web.config:
<setting name="AccountNameValidation" value=".+" />
When using the users email address as username, you should consider changing the membership provider in Sitecore to require a unique email. Otherwise you risk having users that share email addresses.
The change is simple. Go to web.config and change the attribute “requiresUniqueEmail” to “true“:
<add name="sql" type="System.Web.Security.SqlMembershipProvider" connectionStringName="core" applicationName="sitecore" minRequiredPasswordLength="1" minRequiredNonalphanumericCharacters="0" requiresQuestionAndAnswer="false" requiresUniqueEmail="true" maxInvalidPasswordAttempts="256" />