My Sitecore site requires usernames to be email address.
I can create the users successfully in code but whenever I try to create extranet users manually within the Sitecore CMS on the User Manager it throws a valuation error for email usernames user name is not valid in the selected domain.. It appears to be the @ symbol that causes the validation.
How can I update this validation?
Above suggests are correct but I found mine included in an sub config located at
App_Config/Security/Domains.config
<setting name="AccountNameValidation" value=".+" />
Original answer here http://klenke.org/?p=144