Index: django/contrib/auth/models.py
===================================================================
--- django/contrib/auth/models.py	(revision 6426)
+++ django/contrib/auth/models.py	(working copy)
@@ -108,7 +108,12 @@
     def create_user(self, username, email, password=None):
         "Creates and saves a User with the given username, e-mail and password."
         now = datetime.datetime.now()
-        user = self.model(None, username, '', '', email.strip().lower(), 'placeholder', False, True, False, now, now)
+        email_addr = email.strip()
+        email_user_idx = email.find('@')
+        email_user = email_addr[0:email_user_idx]
+        email_domain = email_addr[email_user_idx:len(email_addr)].lower()
+        email_addr_final = u'%s%s' % (email_user, email_domain)
+        user = self.model(None, username, '', '', email_addr_final, 'placeholder', False, True, False, now, now)
         if password:
             user.set_password(password)
         else: