Class SieveMessageError

              object --+                
                       |                
exceptions.BaseException --+            
                           |            
        exceptions.Exception --+        
                               |        
                     PologyError --+    
                                   |    
                          SieveError --+
                                       |
                                      SieveMessageError

Exception for single messages.

If sieve's process method throws it, client is allowed to send other messages from the same catalog to the sieve.