=== modified file 'src/postorius/views/user.py'
--- src/postorius/views/user.py	2013-10-22 18:52:15 +0000
+++ src/postorius/views/user.py	2014-03-19 14:02:30 +0000
@@ -257,15 +257,23 @@
             user = MailmanUser(display_name=form.cleaned_data['display_name'],
                                email=form.cleaned_data['email'],
                                password=form.cleaned_data['password'])
+            user_obj = None
             try:
-                user.save()
-            except MailmanApiError:
-                return utils.render_api_error(request)
-            except HTTPError, e:
-                messages.error(request, e)
+                user_obj = MailmanUser.objects.get(address=form.cleaned_data['email'])
+            except Mailman404Error:
+                user_obj = None
+            if user_obj is not None:
+                messages.error(request, _("User with this e-mail already registered"))
             else:
-                messages.success(request, _("New User registered"))
-            return redirect("user_index")
+                try:
+                    user.save()
+                except MailmanApiError:
+                    return utils.render_api_error(request)
+                except HTTPError, e:
+                    messages.error(request, e)
+                else:
+                    messages.success(request, _("New User registered"))
+                return redirect("user_index")
     else:
         form = UserNew()
     return render_to_response('postorius/users/new.html',