[exim] Equivalent of Envelope-to as variables in pipe transp…

How do I access the equivalent of "Envelope-to" header in transport
variables?

I'm trying to call dovecot-lda in a manner that enables its "envelope"
rule.

To do so requires the MTA to pass information about the envelope recipient
using the -a flag.

Documentation [1] suggests:

  dovecot_delivery:
    driver = pipe
    command = /usr/local/libexec/dovecot/deliver -k \
                  -a "$original_local_part@$original_domain"
    envelope_to_add

But these variables are considered tainted and I cannot see an equivalent.

What is available is $local_part_data and $domain_data, but these diverge
from Envelope-to (eg. on /etc/alias changing the destination)

Or, since I'm merely passing this information down the pipeline (not
deriving a name for files/folders etc.), is it safe to use the tainted
variables and is there some way to safely escape them?

There's a workaround of asking Dovecot to pick up from the header (using
lda_original_recipient_header), but a tidy and proper solution would seem
to avoid modifying the message with a new header.

Exim is v4.97.1 on FreeBSD 13.2

[1] https://doc.dovecot.org/3.0/configuration_manual/howto/dovecot_lda_exim/

--
Mark



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