[Exim] filtering during the data phase

My previous message leads me to ask about filtering being handled differently. At
present the SMTP phase is completed before the filter is run. That means that any
rejection caused by the filter can only be returned to the sender if the sender is
not spoofed. These days "MAIL FROM: <>" seems to be the standard means of sending
out viruses, so it is MAILER-DAEMON at the receiving site which gets them all.

Exim provides for the header recipient and sender fields to be checked during the
SMTP data phase and produce a 550 response at the end. It would be nice if system
filters could be run during this phase too. That way the problem of sorting out
bounced messages would remain with the sending site, not the receiving site.

Any chance of such a change for Exim 4?

Phil.
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Phil Chambers (postmaster@???)
University of Exeter