On Sat, 29 Mar 2003, David Saez wrote:
> > It's not so easy. Think about it, 2 exim installations, both try to do a
> > sender callout with a custom envelope from. This will result in a endless
> > loop (theoretical). Exim would need to handle the outgoing address in a
> > special way (not impossible, but still, less than perfect).
>
> well, I could setup a special address for this (i.e. callout@???)
> for which I will disable sender callout verification so it will never
> enter and endless loop.
I have two reasons for not implementing different senders for callouts:
1. Callout is supposed to be checking that a bounce message can be
delivered to the sender. That is the whole idea of sender verification;
it implements the rule "I won't accept a message unless I can deliver a
bounce if I can't deliver it."
2. Allowing different senders is far too risky because of the problem of
loops. I suspect (actually, I *know* :-) that people would turn it on
without considering the possibility of loops, and there would be endless
trouble. The only possiblity would be to disable callout verification
in the code for the special address (i.e. don't rely on the admin
configuring it). I do not like this (a) because it is so hacky and
special-case, but also (b) because it doesn't conform to my point 1
about bounce messages, as explained above.
--
Philip Hazel University of Cambridge Computing Service,
ph10@??? Cambridge, England. Phone: +44 1223 334714.
