Don't forget to tell Django the session has been modified.

modoboa/extensions/webmail/views.py

@@ -503,7 +503,6 @@ def index(request):
 
     """
     action = request.GET.get("action", None)
-
     if action is not None:
         if not action in globals():
             raise UnknownAction

modoboa/lib/webutils.py

@@ -183,6 +183,7 @@ class NavigationParameters(object):
                     del navparams[param]
                 continue
             navparams[param] = re.escape(value) if escape else value
+        self.request.session.modified = True
 
     def get(self, param, default_value=None):
         """Retrieve a navigation parameter.