[courier-users] Using courierfilter to modify outbound mail

[MK <mk...@co...>]

I'd like to write a basic outbound mail filter to add a DKIM-signature.    I am aware of 
zdkimfilter but it does not really suit my context, and the protocol looks simple enough
that to do what I need here would not  be very difficult.   

I know that courierfilter applies to  inbound messages, but (as per previous posts on
 this list) every message comes in before it goes out.  I've looked at the docs for 
pythonfillter, and it appears that there is the potential to add new headers; I will
probably use this framework.

However, doing a minimal DKIM hash of the From and body is dependent on those fields
not subsequently changing.  I have read in some posts that courier may do some re-writing
or re-structuring.  Is there a potential problem here, or am I good to go?

Sincerely, 
Mark Eriksen