"There are multiple Reply-To 550-5.7.1 headers" when sending to external (contacts) group members hosted their mailbox at gmail

[RobertSchuster]

When I send to groups, external recipients with gmail addresses are rejected.
The failure code from the gmail-server is: There are multiple Reply-To 550-5.7.1 headers
Here is a log extract with anonymized recipient addresses:

2024-11-17T00:33:42.386021+01:00 mail01 postfix/smtp[1803080]: Trusted TLS connection established to gmail-smtp-in.l.google.com[108.177.15.26]:25: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256
2024-11-17T00:33:42.468437+01:00 mail01 postfix/smtp[1803085]: Trusted TLS connection established to mx01.t-online.de[194.25.134.72]:25: TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (secp384r1) server-signature RSA-PSS (4096 bits) server-digest SHA256
2024-11-17T00:33:42.657553+01:00 mail01 postfix/smtp[1803085]: EB9336150E: to=<[email protected]>, relay=mx01.t-online.de[194.25.134.72]:25, delay=0.69, delays=0.11/0.16/0.3/0.12, dsn=2.0.0, status=sent (250 2.0.0 Message accepted.)
2024-11-17T00:33:42.657867+01:00 mail01 postfix/smtp[1803085]: EB9336150E: to=<[email protected]>, relay=mx01.t-online.de[194.25.134.72]:25, delay=0.69, delays=0.11/0.16/0.3/0.12, dsn=2.0.0, status=sent (250 2.0.0 Message accepted.)
2024-11-17T00:33:42.799251+01:00 mail01 postfix/smtp[1803080]: EB9336150E: to=<[email protected]>, relay=gmail-smtp-in.l.google.com[108.177.15.26]:25, delay=0.76, delays=0.11/0.01/0.37/0.28, dsn=5.7.1, status=bounced (host gmail-smtp-in.l.google.com[108.177.15.26] said: 550-5.7.1 This message is not RFC 5322 compliant. There are multiple Reply-To 550-5.7.1 headers. To reduce the amount of spam sent to Gmail, this message has 550-5.7.1 been blocked. For more information, go to 550-5.7.1 https://support.google.com/mail/?p=RfcMessageNonCompliant and review 550 5.7.1 RFC 5322 specifications. ffacd0b85a97d-3821ae3228asi3952477f8f.474 - gsmtp (in reply to end of DATA command))
2024-11-17T00:33:42.830604+01:00 mail01 postfix/qmgr[658]: EB9336150E: removed

In the example, I had a total of 4 list members. One within the grommunio domain, 3 with external/foreign email addresses (contacts).
The grommunio users mail was deliverd to his grommunio mailbox as expected. Of the external ones, 2 were delivered without errors, the third (gmail) came back with the error message mentioned.
The sending mail server (not the grommunio server) has been processing the sending domain for years and is also "responsible" for around 20 other domains and can also talk to gmail. So I don't think there is a fundamental misconfiguration.
The error message also clearly refers to: "There are multiple Reply-To 550-5.7.1 headers, which IMHO indicates a problem with the composition of the mail.

Web UI: 3.1.0-36-gb3e1844
API: 1.16.1
Backend: 1.16.2
Daabase: 131

[jengelh]

I just can't see how we could possibly generate multiple Reply-To lines currently. There is just one place where one header is generated (possibly with multiple addresses, but all in one header/logical line).

        if (oxcmail_export_reply_to(pmsg, *adrlist))
                if (!phead->set_field("Reply-To", adrlist->generate().c_str()))
                        return FALSE;

Gmail SMTP accepts Reply-To with multiple addresses. It also accepts mails with an embedded message attachment which (erroneous) multiple Reply-To (which is ok because it's an attachment).

So, do export the message as MT, e.g. gromox-exm2eml --mt -u sendername@abc 0x12345 >mail.bin.
(find the object ID in g-web with RightClick > Options).
Send the binfile to me privately or to Grommunio support with link to this ticket.

[RobertSchuster]

Unfortunately, I can no longer export the email because emails were constantly being sent and deleted on the test system. Completely incomprehensibly, the email did not end up in the archive system (Benno mail archive), even though the relay server recorded its delivery in the log.
Funny enough, the effect described occurred exactly twice and never again since then. The distribution list (group) used has not changed since then and emails are delivered to the member with the gmail address without any problems.
I now think that the error must unfortunately be considered non-reproducible and perhaps has a different cause - see below.

However, I have been able to reproduce another strange behavior in connection with distribution lists.
In this case, the scenario looks like this:

• Distribution list with only external members who are all created as contacts
• The list works and can be addressed externally as well as internally
• I create a new contact and add it directly to the list
• I then send an email to this list from a Grommunio mailbox
• The email is sent by the web client without errors, but is not delivered to a single recipient. There is no indication that something could have gone wrong.
• Only in the log of "Gromox delivery" can you find:

[2024-11-26 13:13:05.059848]: vmime.send: Error while executing command 'RCPT TO:<[email protected]>'.
[2024-11-26 13:13:05.061856]: E-2134: cu_send_mail: Message was cancelled (e.g. incomplete Envelope-From/Ev-To)

The list will probably work again by itself after a few hours (I think), if you restart the "Gromox delivery" daemon it will work immediately.
It is possible that my first problem is "somehow" related to the second. Unfortunately, I no longer know how static the first distribution list was at the time of sending.
However, the reason for the failure here also seems to be an incorrectly/incompletely created envelope.

The two errors may be related.
Unlike the first case, the second can be reproduced at any time!

[jengelh]

ok so can't repro Reply-To.