Pigeonhole vacation and envelope extension recipient addresses

[David Zambonini]

I have a situation where my LMTP RCPT TO: goes to a mailbox user account that
does not reflect either the final (through aliasing) or envelope email address.

SMTP RCPT TO:    (envelope-local-part at envelope-domain)
Final Recipient: (final-local-part at final-domain)
LMTP RCPT TO:    (mailbox-local-part at mailbox-domain)

I'd like to use the final recipient as the vacation address, but also have the
envelope recipient address used in place of the LTMP RCPT TO for the envelope
extension.

At the moment it looks like I can set one or the other?

Let's say I add an x-final-to and x-envelope-to header to the email headers
before delivering via LMTP.

Then, setting:

sieve_vacation_use_original_recipient = yes
lda_original_recipient_header         = x-final-to

will get the vacation replies coming from where I'd like, but the envelope
extension will not reflect the original SMTP envelope to.

Conversely, setting:

lda_original_recipient_header         = x-envelope-to

might get the envelope extension working correctly, but will not give vacation
replies from where I'd like.

Is there some way anyone is aware of to configure both final and envelope
senders based on email headers (that doesn't involve lda flags, these are on
different systems), or am I currently out of luck? I've tried playing with DSN
ORCPT but it seems like a non-starter trying to get it passed through (exim)

-- 
David Zambonini