John Leslie writes:
It may be worth noting that sender address rewrite should not be
done when forwarding a message via TBR.
(I can't offhand think of a reason you'd actually want to...)
Sieve processors executing redirect statement are permitted to change
the MAIL FROM, or leave it. There are arguments in favour of both
behaviours. If it's changed, it'll probably be to teh owner of the
sieve script, or to <>.
Arnt