uucp and preserving Reply-to: how?

[lark at world.std.com (Lar Kaufman)]

A solution used by some mailhosts is to support the % character, suppressing
resolution of any other part of the address until one or the other side of
the % is used as the forwarding address.  The next site then deals with the
now "normal" address for its network.  However, implementation of this 
seems to be also undefined.

-lar
 Lar Kaufman      Beneath a hill, low in the drowsy willows,
 lark at walden.com  A hundred frogs invisible and clear
 Running Linux    Have propped themselves on green convenient pillows
 BUSL '98         To blow their flutes and say that spring is near. -E.B. White