removing Delivered-To header...?

[Peter Cavender]

Hi-

I have a qmail server hosting several virtual domains, and all mail 
delivered to recipients in the virtual domains have a Delivered-To 
header line indicating the "main" domain name of the server.

I want to delete this line, and I understand that the -d option to 
preline is the way to do this, but *where* do do do this?

TIA

--Pete