We've debugged your logs, and found no major issue in them. The email samples your forwarded us the other day look like spam that SpamFilter was simply unable to stop. We've however checked your logs a bit more in detail to get a "big picture" and see overall how your SpamFilter is performing. This is what we see.
On Feb 5, SpamFilter received 258,474 connection attempts. Of these, a huge amount, 236,414 were rejected. That means 91.5% of your incoming connection attempts in 24 hours were rejected.
Out of the 258,474 email attempts, SpamFilter accepted and forwarded 18,005 of them. However 6,066 of these forwarded emails where whitelisted for some reason, leaving only 11,939 emails that were delivered as they were not detected to be spam. That's 11,939 emails out of 258,474, which is only 4.6% of your total incoming traffic. This means that SpamFilter is detecting as "clean" only 4.6% of your incoming emails, and is blocking the rest (unless whitelisted).
To put things into another perspective, assume that, possibly inflating this number and making it pessimistic, one out of every five emails you receive in your mailbox is spam (as are the samples you sent us). If 1 out of 5 emails that are received is spam, that means that SpamFilter is missing, not blocking, 2,388 (11,939 / 5) emails each day. However 2,388 emails out of 258,474 connection attempts equates to 0.9%. This means that SpamFilter is stopping 99.1% of your spam, which is a very good accuracy rate.
We know everyone would like for this number to be 100% accuracy, but unfortunately I do not think any software will be able to be that accurate.