Submission: track authenticated_user

Hello,

We would like to use Dovecot Submission to have less queues to maintain. The relayhost (Postfix) after Dovecot routes mail by sender_map, so authenticated user, not the "mail from" because .

For what we've seen, we can't use receive header to retrieve this authenticated_user.

Example of header :

 Received: from mailhost ([0.0.0.0])
 by submission.host with ESMTPSA
 id submission-id
 (envelope-from<myadress@example.com>)
 for<myadress@example.com>; Thu, 9 Nov 2022 08:27:41 +0000

So we've thought to use X-client, but reading the doc seems that's not the a good way : /https://doc.dovecot.org/settings/core//

- submission_relay_trusted         
     If enabled, the relay server is trusted.
     Determines whether we try to send (Postfix-specific) XCLIENT data to the
     relay server (only if enabled).

But, XCLIENT for Submission seems to not transfer LOGIN : /https://doc.dovecot.org/settings/core/ /

 XCLIENT command can be used to override:
     Session ID
     Client IP and port (|%{rip}|,|%{rport}|)
     HELO - Overrides what the client sent earlier in the EHLO command
     LOGIN - Currently unused
     PROTO - Currently unused

|forward_*|  fields can be sent to auth process’s passdb lookup

The trust is always checked against the connecting IP address.
Except if HAProxy is used, then the original client IP address is used.

Do you know another way to inform the relayhost of submission of the authenticated_user?

Thanks

Ismaël TANGUY