old_contents: from django.conf.urls import url
  
  from .views import MessageCreateView, ThreadDetailView, ThreadListView
  
  urlpatterns = [
      url(r'^(?P<recipient>[a-zA-Z0-9_]+)/$', ThreadDetailView.as_view(),
          name='thread-detail'),
      url(r'^(?P<pk>\d+)/new/$', MessageCreateView.as_view(),
          name='new-message'),
      url(r'^$', ThreadListView.as_view())
  ]
  
new_contents: from django.conf.urls import url
  
  from .views import MessageCreateView, ThreadDetailView, ThreadListView
  
  urlpatterns = [
      url(r'^@(?P<recipient>[a-zA-Z0-9_]+)/$', ThreadDetailView.as_view(),
          name='thread-detail'),
      url(r'^(?P<pk>\d+)/new/$', MessageCreateView.as_view(),
          name='new-message'),
      url(r'^$', ThreadListView.as_view())
  ]
  
subject: Use `@` in message thread