Hi Kenneth.
The message looks like this. It originated from a RCS client and is stored in Cyrus in RFC5322 format for archival purposes.
From: sip:15554441001@xxxxxxxxxxxx To: sip:15554441003@xxxxxxxxxxxx Date: Wed, 31 Mar 2021 15:33:16+0000 Conversation-ID: Conversation-TestCase9 Contribution-ID: Contribution-TestCase9 IMDN-Message-ID: Test 9-903 Content-Type: Message/CPIM From: sip:15554441001@xxxxxxxxxxxx To: <sip:anonymous@anonymous.invalid> DateTime: 2021-03-31T15:33:16Z NS: imdn <urn:ietf:params:imdn> imdn.Message-ID: Test 9-903 imdn.Disposition-Notification: positive-delivery, display Content-Type: text/plain Content-Length: 13 Hello, test 9
BTW, thunderbird has no problem pulling this from the server and displays it using IMAP.