I wanted to do some tests against a zombie NPC using a weapon with Smite. However, it seems that smite does not affect the zombie NPCs at all, as they don't take extra damage from my weapons like normal zombies would. Any idea how to fix this? Is there a feature in the NPC config I'm missing?

Thanks for the report. The NPCs has currently no Mob Type, however of the Enchantment are based on the Mob Type.

I will add the basic mob types with the next update, so that all enchantment should have the same effect on the NPCs.