How many messages do you receive per day?
The reason I ask is these filters will add additional load on your SME server, so make sure it is up to the task. I have similar setups that do this alone (not used for anything else).
I had one server choke when a hub died. When I relaced the hub, the internal mail server spewed a bunch of messages the the gateway and down she went (my fault).
Needless to say, I upgraded the hardware to be on the safe side.
Check the logs and let us know.
There may be some messages still in the server at various stages of processing. There is a contrib that allows you to view messages in the queue.
Shane