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Microsoft Teams Meeting invitation forwarding

Hi everyone

Microsoft Teams Meeting invitation contains a link to the meeting. If
you want to add someone new to the meeting, you forward the appropriate
calendar item which generates two emails, one to the new invitee and the
second one to the original meeting organizer.

Problem is, at least in our setup, that email to the new invitee gets
rejected, with the following error message in SMTP-In log:
    550 5.7.0 Authentication rejected
    Authentication does not match address found in FROM header

The problem is, as far as I can see, the following. This is a new
invitee message header:
*******************************************
Date: Mon, 08 Mar 2021 14:05:00 +0100
From: "Original Sender" <Original.Sender@domain_1.com>
Sender: "Original Recipient" <Original.Recipient@domain_2.com>
Subject: FW: Microsoft Teams Meeting
To: "New Invitee 1" <New.Invitee.1@domain_3.com>,
     "New Invitee 2" <New.Invitee.2@domain_4.com>
Message-ID: <c0f9fee8.1d7141b.15a6231.4cc6@domain_1.com>
X-Priority: 3
X-MS-TNEF-Correlator: Sest-0wB38d5K-kPB2tIzZLqgXE5qAeRm6NuAK8fn5ZINxT
X-Mailer: MDaemon Connector 7.0.2
MIME-Version: 1.0
Content-Type: multipart/mixed;
        boundary="----=_NextPart_000_0028_01D71424.22B98240"
X-MS-TNEF-Correlator: Sest-0wB38d5K-kPB2tIzZLqgXE5qAeRm6NuAK8fn5ZINxT

This is a multipart message in MIME format.

------=_NextPart_000_0028_01D71424.22B98240
Content-Type: text/plain;
        charset="iso-8859-2"
Content-Transfer-Encoding: quoted-printable

Dear Sir/Madam
Please join the below Microsoft Meeting

Regards

-----Original Appointment-----
From: "Original Sender" <Original.Sender@domain_1.com>
Sent: Monday, March 8, 2021 10:58 AM
To: "Original Recipient" <Original.Recipient@domain_2.com>; Original
Recipient B; Original Recipient C
Subject: Microsoft Teams Meeting
When: Tuesday, 09. March 2021. 10:00-11:30 (UTC+01:00) Amsterdam, Berlin,
Bern, Rome, Stockholm, Vienna.
Where: Microsoft Teams Meeting
...
*******************************************

In this case, we are domain_2.com and forwarded message keeps original
sender (Meeting organizer) in the From field.
What should be done to allow messages like this to pass?

Regards

(older msg: 2)

Aleksandar Devecerski - Mar 8, 2021 1:34 pm (#3 Total: 5)

Aleksandar Deve…

Newbie
Posts: 47

Hello Arron
Thanks for the quick response

One more thing before doing what you suggested. There's a whitelist for
the SMTP Authentication, CredsMatchWhiteList.dat.
Note says:
# This file lists IP and email addresses that are exempt from the
requirements that
# the authentication credentials presented during SMTP AUTH match the
address found
# in the return-path or 'From:' header.

Back to my original example. In order to make this work, should I add to
the whitelist
- Original Sender" <Original.Sender@domain_1.com> -> meeting
organizer who invited my user, or
- Original Recipient" <Original.Recipient@domain_2.com> -> my user who
invited another two people to the meeting he was invited?

I prefer using whitelist(s) because it gives me some measure of control
over things. If I can add a list of selected meeting organizers here (if
option one above is correct) that would be really good, because in our
case this is not such a big list.
If option 2 is correct I would basically have to whitelist all local
users, giving up one of the tools used to fight various characters on
the Net posing as my local users.

Regards

Arron Caruth - Mar 8, 2021 3:43 pm (#4 Total: 5)

Guest User

Posts: 1

If you want to whitelist addresses, you would need to whitelist the address that is in the From header. if we go back to your original example, you would need to add Original.Sender@domain_1.com to the whitelist.

--
Arron Caruth
Vice President of Product Development
o: 817-601-3222 e: Arron.Caruth@mdaemon.com

MDaemon Technologies
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Visit us on www.mdaemon.com | Facebook | LinkedIn | YouTube
Sent using the MDaemon Email Server

On Mon, 8 Mar 2021 13:34:29 -0500, "lists-md-issues@mdaemon.com (Aleksandar Devecerski)" <lists-md-issues@mdaemon.com> wrote:
Hello Arron
Thanks for the quick response

One more thing before doing what you suggested. There's a whitelist for
the SMTP Authentication, CredsMatchWhiteList.dat.
Note says:
# This file lists IP and email addresses that are exempt from the
requirements that
# the authentication credentials presented during SMTP AUTH match the
address found
# in the return-path or 'From:' header.

Back to my original example. In order to make this work, should I add to
the whitelist
- Original Sender" <Original.Sender@domain_1.com> -> meeting
organizer who invited my user, or
- Original Recipient" <Original.Recipient@domain_2.com> -> my user who
invited another two people to the meeting he was invited?

I prefer using whitelist(s) because it gives me some measure of control
over things. If I can add a list of selected meeting organizers here (if
option one above is correct) that would be really good, because in our
case this is not such a big list.
If option 2 is correct I would basically have to whitelist all local
users, giving up one of the tools used to fight various characters on
the Net posing as my local users.

Regards

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--------------------------------------------------------------------------
These forums are provided by MDaemon Technologies for user-to-user
support and discussion.  MDaemon staff members may participate in the
forums periodically but please recognize that this is not the official
method of receiving technical support. To receive personal technical
support please use the form here:
http://www.mdaemon.com/Support/RequestSupport/
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Aleksandar Devecerski - Mar 8, 2021 4:29 pm (#5 Total: 5)

Aleksandar Deve…

Newbie
Posts: 47

I'll try whitelist first and, if that does not help, unchecking
'Credentials used must match those of the From: header address'.

Thank you