FutureQuest does employ real time blacklist filtering at the network edge to prevent spam from overwhelming the mail servers.
The below Community Forum post discusses when it was employed and the situation behind the decision to use blacklist filtering:
The following blacklists are currently being used in the order listed:
UCE Level 1: UCEPROTECT Blacklist LEVEL 1
Barracuda Central : Barracuda Reputation Block List (BRBL)
Note: FutureQuest monitors several blacklist services closely and may modify them as required to ensure the best service possible.