First, if you are not using the latest version of SNF then please upgrade (you can do this by visiting our Downloads page and downloading the latest version). There are a number of things you might do depending upon your system's abilities, policies and tolerance for false positives.

1. Be sure you are updating your rulebase each time you receive an update notification. This can/should be done automatically.
2. Be sure we are getting copies of spam that do get through on your system. The best way to do this is to set up a mailbox on your system that our bots can pull from using POP3 and to forward any missed spam to that mailbox.
3. If there are character sets or other common characteristics of troublesome spam on your system and you also do not have any legitimate mail that contains those character sets then let us know and we will create local black rules for your system to block these.
4. SNF on its own is very good, but not perfect ;-) Be sure you are also making the best use of other tests that are available (most of them free).

--- Filtering spam is a tough business... To start with, the spammers these days are testing all of their messages against existing filters to be sure they will get through before they are sent, and then they send those messages in huge spikes through distributed bot networks to maximize the damage they can do before filters adapt.

If you have any special insights to the spam that is still leaking in your system - in particular, if there is anything that you can filter out because you would never expect any legitimate messages with a particular characteristic - then let us know and we will work with you to develop additional black rules specifically for your system.