This follows from my earlier messages with the same subject.
It appears that $original_local_part expands to "message filter" when a message has
been generated by a "deliver" command in a system filter. In practice this means
that it may not be possible to use $original_local_part when using a system filter
which uses "deliver".
I can see two alternatives:
1) When using $original_local_part, make it conditional:
${if eq {$original_local_part}{message filter}\
{$local_part}{$original_local_part}}
so that a legal result is always obtained.
2) Make Exim evaluate $original_local_part in this way automatically.
In the first case the documentation for $original_local_part should point out this
potential problem.
(I presume the same can be said for $parent_local_part too.)
Phil.
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Phil Chambers (postmaster@???)
University of Exeter