Re: [Exim] Sender callout verification issues

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Author: Philip Hazel
Date:  
To: I. Forbes
CC: exim-users
Subject: Re: [Exim] Sender callout verification issues
On Wed, 5 Nov 2003, I. Forbes wrote:

> Can exim be setup to use an alternate address in an additional test
> if the sending server rejects "MAIL FROM: <>" ?


This has been requested before. The answer is "no", and I don't think
this is a sensible thing to do. One reason has already been posted - it
may cause loops. The other reason is as follows:

The whole point of sender verification is to try to find out if it would
be possible to deliver a bounce message to the sender address, before
accepting a message. That is, you want to know the answer to "If I
accept this message, and then have a delivery problem later, could I
send back a bounce to the sender?" If the answer is "no", you reject the
message. (You can never be sure that the answer is "yes", of course, but
at least "maybe" is better than no knowledge.)

A bounce message will be sent with MAIL FROM:<> so that is what is used
for testing.

--
Philip Hazel            University of Cambridge Computing Service,
ph10@???      Cambridge, England. Phone: +44 1223 334714.
Get the Exim 4 book:    http://www.uit.co.uk/exim-book