Recognize MS Exchange read receipts as read receipts

They contain X-MSExch-Correlation-Key header, but no
Original-Message-ID, so they cannot be used to find the original
message, but we want to recognize them as MDN nevertheless to assign
them to the trash chat.

src/mimeparser.rs

@@ -1159,23 +1159,21 @@ impl MimeMessage {
 
         // must be present
         if let Some(_disposition) = report_fields.get_header_value(HeaderDef::Disposition) {
-            if let Some(original_message_id) = report_fields
+            let original_message_id = report_fields
                 .get_header_value(HeaderDef::OriginalMessageId)
-                .and_then(|v| parse_message_id(&v).ok())
+                .and_then(|v| parse_message_id(&v).ok());
-            {
+            let additional_message_ids = report_fields
-                let additional_message_ids = report_fields
+                .get_header_value(HeaderDef::AdditionalMessageIds)
-                    .get_header_value(HeaderDef::AdditionalMessageIds)
+                .map_or_else(Vec::new, |v| {
-                    .map_or_else(Vec::new, |v| {
+                    v.split(' ')
-                        v.split(' ')
+                        .filter_map(|s| parse_message_id(s).ok())
-                            .filter_map(|s| parse_message_id(s).ok())
+                        .collect()
-                            .collect()
+                });
-                    });
 
-                return Ok(Some(Report {
+            return Ok(Some(Report {
-                    original_message_id,
+                original_message_id,
-                    additional_message_ids,
+                additional_message_ids,
-                }));
+            }));
-            }
         }
         warn!(
             context,
@@ -1331,8 +1329,10 @@ impl MimeMessage {
         parts: &[Part],
     ) {
         for report in &self.mdn_reports {
-            for original_message_id in
+            for original_message_id in report
-                std::iter::once(&report.original_message_id).chain(&report.additional_message_ids)
+                .original_message_id
+                .iter()
+                .chain(&report.additional_message_ids)
             {
                 match message::handle_mdn(context, from_id, original_message_id, sent_timestamp)
                     .await
@@ -1437,7 +1437,10 @@ async fn update_gossip_peerstates(
 #[derive(Debug)]
 pub(crate) struct Report {
     /// Original-Message-ID header
-    original_message_id: String,
+    ///
+    /// It MUST be present if the original message has a Message-ID according to RFC 8098, but MS
+    /// Exchange does not add it nevertheless, in which case it is `None`.
+    original_message_id: Option<String>,
     /// Additional-Message-IDs
     additional_message_ids: Vec<String>,
 }
@@ -2346,7 +2349,7 @@ Additional-Message-IDs: <foo@example.com> <foo@example.net>\n\
         assert_eq!(message.mdn_reports.len(), 1);
         assert_eq!(
             message.mdn_reports[0].original_message_id,
-            "foo@example.org"
+            Some("foo@example.org".to_string())
         );
         assert_eq!(
             &message.mdn_reports[0].additional_message_ids,
@@ -3125,4 +3128,18 @@ Message.
 
         Ok(())
     }
+
+    /// Test parsing of MDN sent by MS Exchange.
+    ///
+    /// It does not have required Original-Message-ID field, so it is useless, but we want to
+    /// recognize it as MDN nevertheless to avoid displaying it in the chat as normal message.
+    #[async_std::test]
+    async fn test_ms_exchange_mdn() -> Result<()> {
+        let t = TestContext::new_alice().await;
+        let raw =
+            include_bytes!("../test-data/message/ms_exchange_report_disposition_notification.eml");
+        let mimeparser = MimeMessage::from_bytes(&t.ctx, raw).await?;
+        assert!(!mimeparser.mdn_reports.is_empty());
+        Ok(())
+    }
 }

test-data/message/ms_exchange_report_disposition_notification.eml

@@ -0,0 +1,108 @@
+Return-Path: <anonymous@example.org>
+Delivered-To: anonymous@posteo.de
+Received: from proxy02.posteo.name ([127.0.0.1])
+	by dovecot16.posteo.name (Dovecot) with LMTP id Cp2uFxP1sWHbCQEAchYRkQ
+	for <anonymous@posteo.de>; Thu, 09 Dec 2021 13:25:38 +0100
+Received: from proxy02.posteo.de ([127.0.0.1])
+	by proxy02.posteo.name (Dovecot) with LMTP id MWsaCwrvsWG0wgEAGFAyLg
+	; Thu, 09 Dec 2021 13:25:38 +0100
+Received: from mailin06.posteo.de (unknown [10.0.1.6])
+	by proxy02.posteo.de (Postfix) with ESMTPS id 4J8tXy0KkMz120l
+	for <anonymous@posteo.de>; Thu,  9 Dec 2021 13:25:38 +0100 (CET)
+Received: from mx04.posteo.de (mailin06.posteo.de [127.0.0.1])
+	by mailin06.posteo.de (Postfix) with ESMTPS id F24DE215B8
+	for <anonymous@posteo.de>; Thu,  9 Dec 2021 13:25:37 +0100 (CET)
+X-Virus-Scanned: amavisd-new at posteo.de
+X-Spam-Flag: NO
+X-Spam-Score: 0.011
+X-Spam-Level: 
+X-Spam-Status: No, score=0.011 tagged_above=-1000 required=7
+	tests=[HTML_MESSAGE=0.001, T_POSTEO_TLSINY=0.01] autolearn=disabled
+X-Posteo-Antispam-Signature: v=1; e=base64; a=aes-256-gcm; d=27yedFdXeAzOobR4x685XJ/5e6WQmX8PP5pSnOlGU2a9Ismhk38wb5AS44xh1yeL5PUxla78UEsHwGkPR0IyPRlHWaLMFLd5CJZN3GzFfrj/2CuB+cd1hOLpp9hRmCebc3rchuDr
+Authentication-Results: posteo.de; dmarc=none (p=none dis=none) header.from=example.org
+X-Posteo-TLS-Received-Status: TLSv1.2
+Received: from mail.example.org (mail.example.org [0.0.0.0])
+	by mx04.posteo.de (Postfix) with ESMTPS id 4J8tXx38vRz10yw
+	for <anonymous@posteo.at>; Thu,  9 Dec 2021 13:25:37 +0100 (CET)
+Received: from [192.168.1.11] (port=22105 helo=mail.example.org)
+	by mail.example.org with esmtps  (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384
+	(Exim 4.94.2)
+	(envelope-from <anonymous@example.org>)
+	id 1mvIUG-0007VC-2U
+	for anonymous@posteo.at; Thu, 09 Dec 2021 13:25:24 +0100
+From: Anonymous <anonymous@example.org>
+To: Anonymous <anonymous@posteo.at>
+Subject: Gelesen: Test message
+Thread-Topic: Test message
+Thread-Index: AQHX7Dt/+5f88Aokk0KrqG0hbF8dN6wqFvxh
+Date: Thu, 9 Dec 2021 12:25:24 +0000
+Message-ID: <1711fc3548cd4b2699ccd4fffac17713@anonymous>
+In-Reply-To: <75dd051097b02468183707ad0dd62ebd@posteo.de>
+Accept-Language: de-AT, de-DE, en-US
+Content-Language: de-DE
+X-MS-Has-Attach:
+X-MS-TNEF-Correlator:
+x-ms-exchange-transport-fromentityheader: Hosted
+x-originating-ip: [192.168.120.215]
+Content-Type: multipart/report;
+	boundary="_000_1711fc3548cd4b2699ccd4fffac17713anonymous_";
+	report-type=disposition-notification
+MIME-Version: 1.0
+
+--_000_1711fc3548cd4b2699ccd4fffac17713anonymous_
+Content-Type: multipart/alternative;
+	boundary="_002_1711fc3548cd4b2699ccd4fffac17713anonymous_"
+
+--_002_1711fc3548cd4b2699ccd4fffac17713anonymous_
+Content-Type: text/plain; charset="iso-8859-1"
+Content-Transfer-Encoding: quoted-printable
+
+Ihre Nachricht
+
+   An: Anonymous
+   Betreff: Test message
+   Gesendet: Mittwoch, 8. Dezember 2021 14:57:05 (UTC+01:00) Amsterdam, Ber=
+lin, Bern, Rom, Stockholm, Wien
+
+ wurde am Donnerstag, 9. Dezember 2021 13:24:34 (UTC+01:00) Amsterdam, Berl=
+in, Bern, Rom, Stockholm, Wien gelesen.
+
+--_002_1711fc3548cd4b2699ccd4fffac17713anonymous_
+Content-Type: text/html; charset="iso-8859-1"
+Content-Transfer-Encoding: quoted-printable
+
+<html>
+<head>
+<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Diso-8859-=
+1">
+<meta name=3D"Generator" content=3D"Microsoft Exchange Server">
+<!-- converted from text --><style><!-- .EmailQuote { margin-left: 1pt; pad=
+ding-left: 4pt; border-left: #800000 2px solid; } --></style>
+</head>
+<body>
+<font size=3D"2"><span style=3D"font-size:10pt;">
+<div class=3D"PlainText">Ihre Nachricht <br>
+<br>
+&nbsp;&nbsp; An: Anonymous<br>
+&nbsp;&nbsp; Betreff: Test message<br>
+&nbsp;&nbsp; Gesendet: Mittwoch, 8. Dezember 2021 14:57:05 (UTC&#43;01:00) =
+Amsterdam, Berlin, Bern, Rom, Stockholm, Wien<br>
+<br>
+&nbsp;wurde am Donnerstag, 9. Dezember 2021 13:24:34 (UTC&#43;01:00) Amster=
+dam, Berlin, Bern, Rom, Stockholm, Wien gelesen.</div>
+</span></font>
+</body>
+</html>
+
+--_002_1711fc3548cd4b2699ccd4fffac17713anonymous_--
+
+--_000_1711fc3548cd4b2699ccd4fffac17713anonymous_
+Content-Type: message/disposition-notification
+
+Final-recipient: RFC822; anonymous@example.org
+Disposition: automatic-action/MDN-sent-automatically; displayed
+X-MSExch-Correlation-Key: coNC5vaCQkiAOjek1v1Uew==
+X-Display-Name: Anonymous
+
+
+--_000_1711fc3548cd4b2699ccd4fffac17713anonymous_--