Just a quick note for those running GFI MailEssentials. GFI have released another patch (for version 20070707) to help more with the evolving PDF spam attacks. You can get it here.
It is also recommended that you add 12.apews.dnsbl.uceprotect.net to the DNS Blacklist check. Read more about this blacklist here.
Best antispam technique to come out in years – Greylisting:
http://www.grynx.com/projects/greylist
The Greylist app nukes the Directory Harvesting Attack meail prior to GFI even seeing it.