This is not possible, because the filter frontend supports all kind of 
filter backends, and there is no means to get to Horde's address book 
from a server side filter engine like sieve or procmail.

We could make this available for client side filtering only, but I'd 
imagine that's going to kill performance pretty quickly.

Please add a way to filter email directly on the server by allow the 
user to select in the rules "From" "contains" "only those in my 
address book".



I think this would help me and others who receive THOUSANDS of 
junk/spam/pornographic email each month reduce this problem immensely. 
  In spite of all the other filters I've employed, I feel I must 
resort to this method.



There's also no way to filter iPhone email - this would put you ahead 
of the curve.



Thanks so much-