[exim] In place message alteration

Hi !!

I thinking about altering messages in place (in the spool directory)
running external programs via {run } from data acl, from a router or
externally using a cron job to avoid the overhead of having to run
the external command in a transport which will then reinject and
reroute the message again. Will this cause any major problem to exim ?

--
Thanx & best regards ...

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