Thanks for the suggestion about transport_destination_recipient_limit = 1. I agree this is the right setting when you want Postfix to add X-Original-To in a reliable way.
However, in my setup I am trying to avoid using X-Original-To and similar headers. These headers can be added or changed by remote systems before the message reaches my Postfix. In contrast, ORCPT is part of the local delivery envelope and is set by the final MTA.
My goal is for Dovecot’s LMTP server to always receive ORCPT, so that sieve’s envelope "to" can see the original recipient (as it did before with deliver -a).
At the moment:
Dovecot’s LMTP already accepts and uses ORCPT when it is present.
Postfix only sends ORCPT if the server advertises DSN.
Dovecot’s LMTP does not advertise DSN in its LHLO reply.
This is why I am asking whether LMTP could (optionally) advertise DSN. If it did, Postfix would send ORCPT, and Dovecot/sieve could use the original envelope recipient without depending on X-Original-To.
Thanks,
Dhaval
On (Wed) Oct 21, 2026 5:36 am, Ralf Hildebrandt via dovecot <dovecot@dovecot.org> wrote:
- Dhaval Patel via dovecot <dovecot@dovecot.org>:
Thanks. I tried that route, but Postfix only writes X-Original-To in its own final-delivery agents (local, virtual, pipe); the lmtp client doesn't add it. Of 18 messages delivered over LMTP in the last day, 17 have no X-Original-To, and the one that does carries lists-debian-security-announce@bendel.debian.org, inserted by Debian's list server upstream.
By default, the Postfix SMTP+LMTP client delivers mail to multiple recipients per delivery request. This is undesirable when prepending a Delivered-to: or X-Original-To: message header. To prevent Postfix from sending multiple recipients per delivery request, specify transport_destination_recipient_limit = 1 in the Postfix main.cf file, where transport is the name in the first column of the Postfix master.cf entry for this mail delivery service.
(most likely "lmtp"...)
-- Ralf Hildebrandt Geschäftsbereich IT | Abteilung Netz | Netzwerk-Administration Invalidenstraße 120/121 | D-10115 Berlin Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962 ralf.hildebrandt@charite.de | https://www.charite.de
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Thanks for the suggestion about (->)transport_destination_recipient_limit = 1. I agree this is the right setting when you want Postfix to add
(->)X-Original-To in a reliable way.
However, in my setup I am trying to avoid using (->)X-Original-To and
similar headers. These headers can be added or changed by remote systems
before the message reaches my Postfix. In contrast, ORCPT is part of the
local delivery envelope and is set by the final MTA.
My goal is for Dovecot's LMTP server to always receive ORCPT, so that
sieve's (->)envelope "to" can see the original recipient (as it did
before with (->)deliver -a).
At the moment:
Dovecot's LMTP already accepts and uses ORCPT when it is present.
Postfix only sends ORCPT if the server advertises DSN.
Dovecot's LMTP does not advertise DSN in its LHLO reply.
This is why I am asking whether LMTP could (optionally) advertise DSN. If
it did, Postfix would send ORCPT, and Dovecot/sieve could use the original
envelope recipient without depending on (->)X-Original-To.
Thanks,
Dhaval
On (Wed) Oct 21, 2026 5:36 am, Ralf Hildebrandt via dovecot <dovecot@dovecot.org> wrote: >* Dhaval Patel via dovecot <dovecot@dovecot.org>: >> Thanks. I tried that route, but Postfix only writes X-Original-To in its own final-delivery agents (local, virtual, pipe); the lmtp client doesn't add it. Of 18 messages delivered over LMTP in the last day, 17 have no X-Original-To, and the one that does carries lists-debian-security-announce@bendel.debian.org, inserted by Debian's list server upstream. > >By default, the Postfix SMTP+LMTP client delivers mail to multiple >recipients per delivery request. This is undesirable when prepending a >Delivered-to: or X-Original-To: message header. To prevent Postfix >from sending multiple recipients per delivery request, specify > >transport_destination_recipient_limit = 1 > >in the Postfix main.cf file, where transport is the name in the first >column of the Postfix master.cf entry for this mail delivery service. > >(most likely "lmtp"...) > >-- >Ralf Hildebrandt > Geschaeftsbereich IT | Abteilung Netz | Netzwerk-Administration > Invalidenstrasse 120/121 | D-10115 Berlin > Tel. +49 30 450 570 155 | Fax: +49 30 450 570 962 > ralf.hildebrandt@charite.de | https://www.charite.de >
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