Body signature fails when attaching a message

[shubell]

Versions

• Windows Server Version 2012 r2: [9600]
• Exchange Version 2016 CU16 [15.1.1979.3]
• Installed DKIM Exchange Version: [3.3.1]

Description

When forwarding a mail as attachment dkim signature fails on body

Steps to Reproduce

1. Send a mail from gmail to exchange
2. Forward the recieved mail as attachment in Outlook back to gmail

Signing works if there is no embedded message/rfc822. There is also a possibility that the message has some headers or something that disrupts the signing process. I am including a message to forward. testmessage.zip

[Mbiko]

Was This Issue Resolved

[shubell]

nope

On Wed, 21 Jul 2021, 17:12 Mbiko, @.***> wrote:

Was This Issue Resolved

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[sn3ak]

Also having this issue. Exchange 2016 CU19 [15.1.2176.2] DKIM Exchange Version: [3.3.2]

We found that a rule adding a disclaimer to the email is causing the problem, but only when attachments are included. If you turn off the rule, it works fine. If you turn the rule on and send an email without attachments, it's fine. Rule on and attachment included fails as indicated by OP.

[shubell]

The issue occurs only when the Content-Type is message/rfc822 but if it is application/octet-stream it is ok. So kinda you would be able to change the content type of *.msg to octet-stream the issue would be gone. Also if you digitally sign the outgoing message with a certificate no matter what kind of attachment you add it works ok.