[xwiki-users] Login to XWiki using email address

Hi, Is there a way to login to XWiki using the user's e-mail address. I tried to create a user whose Login ID is equal to his e-mail address. But, it is not possible. I suppose that XWiki doesn't allow the @ character on the Login ID. I know I can extend the XWiki Authentication classes. But I was hoping to find something faster. Thanks, Abel