With the introduction of IPv6 in SmarterMail 11.x, there are a few security and spam checks included within SmarterMail that are exclusively IPv4 based. Below is a list of what is compatible with IPv6 from a security and anti-spam perspective.

IPv6 Anti-virus:
All anti-virus measures within SmarterMail work with IPv6

IPv6 Anti-spam:
Declude
SpamAssassin-based Pattern Matching
Remote SpamAssassin
Cyren
Message Sniffer
Custom Rules
Bayesian Filtering
Domain KeysDKIM
URIBL

IP-based Checks Disabled for IPv6:
SPF
Reverse DNS
RBL

Other Checks Disabled for IPv6:
Greylisting
Black and White Lists
DOS and Brute Force Intrusion Detection