In message <Pine.SOL.3.96.970429095422.19386M-100000@???>,
Philip Hazel writes on the issue of more complex rewrite functionality:
> I don't have the precise general function mentioned above. I seem to
> remember I raised the question of what do you do if "to:" contains more
> than one address, each potentially requiring a different re-write? This
> was what led to the point about another rewrite stage just prior to
> delivery, and as a result, I *do* have on my list the following:
>
> Option to set up a filter to process for deliveries via specific
> transports. Pass message and address(es) to a command and read it
> back. This gives the opportunity for encryption on the fly, and any
> other address-specific munging.
That would be nice for the general case of message transformations.
Since Exim already has header rewriting internally though, it would
be a pity if we couldn't reuse it during delivery. Having said that,
I'm not the one doing the work. :-)
If you do implement the rewrite as an external filter program, Phil,
could you please allow the innards of Exim to communicate state info
to the program? For example, two or more routers may use the same
transport yet require different filtering arrangements in a dynamic
way, eg. as a different function of local_part depending on the router,
and this routing-time info musn't get lost. The approach I would
prefer would be for drivers to be able to define values for arbitrary
named variables which can then affect the expansion of the external
program's command path or flags prior to invocation.
Needless to say, such a general facility would be of use in a million
other places where string arguments are expanded as well. It would be
a real "power feature", defined as one applicable in areas the designer
never envisaged. [There are no power features in MS products. :-)]
Rich.
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