message: fall-back to received for dateless

For the (rare) messages without a Date: header, attempt to guess a date
from the top (most-recent) Received: header. Not perfect, of course, but
better than nothing.

Requires re-indexing to apply to already indexed messages.

Should help for #1083.

NEWS.org

@@ -10,7 +10,12 @@
 
    - significant speed-ups in the cleanup process after ~mu index~ (1.14.0)
 
-   - record the timezone-offset for message sent dates (1.14.3)
+   - Record the timezone-offset for message sent dates as part of the index
+     (1.14.3)
+
+   - for (rare) messages without a =Date:= header, fall-back to the date of the
+     most recent =Received:= header. Not perfect, but better than nothing.
+     Requires re-indexing to apply to older messages (1.14.3)
 
 *** mu4e
 

lib/message/mu-message.cc

@@ -741,7 +741,10 @@ fill_document(Message::Private& priv)
 				doc.add(field.id, priv.ctime);
 			break;
 		case Field::Id::Date:
-			if (const auto& date{mime_msg.date()}; date) {
+			/* for the rare message without a Date: header, fall back
+			 * to the most recent Received: header */
+			if (const auto date{mime_msg.date().or_else([&]{
+					return mime_msg.received(); })}; date) {
 				doc.add(field.id, date->first);
 				doc.add(Field::Id::UtcOffset, date->second);
 			}

lib/message/mu-mime-object.cc

@@ -22,7 +22,9 @@
 #include "gmime/gmime-message.h"
 #include "utils/mu-utils.hh"
 #include "utils/mu-utils-file.hh"
+#include <algorithm>
 #include <mutex>
+#include <ranges>
 #include <regex>
 #include <fcntl.h>
 #include <sys/stat.h>
@@ -334,19 +336,47 @@ MimeMessage::make_from_text(const std::string& text)
 		return make_from_stream(std::move(stream));
 }
 
+static MimeMessage::Date date_from_date_time(GDateTime* dt)
+{
+	constexpr auto usecs_per_sec = 1'000'000;
+	return MimeMessage::Date {g_date_time_to_unix(dt),
+				  g_date_time_get_utc_offset(dt) / usecs_per_sec };
+}
+
+
 Option<MimeMessage::Date>
 MimeMessage::date() const noexcept
 {
 	if (/*const*/GDateTime *dt{g_mime_message_get_date(self())}; !dt)
 		return Nothing;
 	else {
-		constexpr auto usecs_per_sec = 1'000'000;
-		return Date{ g_date_time_to_unix(dt),
-			     g_date_time_get_utc_offset(dt) / usecs_per_sec };
-
+		return date_from_date_time(dt);
 	}
 }
 
+Option<MimeMessage::Date>
+MimeMessage::received() const noexcept
+{
+	const auto recv{header("Received")};
+	if (!recv)
+		return Nothing;
+
+	/* per RFC 5322, "Received:" is *received-token ";" date-time, so the
+	 * date-time follows the _last_ semicolon. */
+	const auto pos{recv->rfind(';')};
+	if (pos == std::string::npos)
+		return Nothing;
+
+	GDateTime *dt{g_mime_utils_header_decode_date(recv->c_str() + pos + 1)};
+	if (!dt)
+		return Nothing;
+
+	const auto date{date_from_date_time(dt)};
+	g_date_time_unref(dt);
+
+	return date;
+}
+
 constexpr Option<GMimeAddressType>
 address_type(Contact::Type ctype)
 {
@@ -372,20 +402,20 @@ address_type(Contact::Type ctype)
 static Mu::Contacts
 all_contacts(const MimeMessage& msg)
 {
-	Contacts contacts;
-
-	for (auto&& cctype: {
+	constexpr auto ctypes = std::to_array({
 			Contact::Type::Sender,
 			Contact::Type::From,
 			Contact::Type::ReplyTo,
 			Contact::Type::To,
 			Contact::Type::Cc,
 			Contact::Type::Bcc
-		}) {
-		auto addrs{msg.contacts(cctype)};
-		std::move(addrs.begin(), addrs.end(),
+		});
+
+	Contacts contacts;
+	std::ranges::move(ctypes | std::views::transform([&](auto ctype) {
+				return msg.contacts(ctype); })
+			         | std::views::join,
 			  std::back_inserter(contacts));
-	}
 
 	return contacts;
 }

lib/message/mu-mime-object.hh

@@ -1051,16 +1051,23 @@ public:
 	/**< Date type */
 
 	/**
-	 * Gets a date, utf-offset pair if it exists, or nullopt otherwise.
+	 * Gets a { date, utf-offset } pair if it exists, or nullopt otherwise.
 	 *
 	 * The date is the number of seconds since epoch (i.e., unix time),
 	 * while utf-offset is the number of seconds offset from UTC
 	 * (i.e., negative numbers west of GMT, positive numbers for east)
 	 *
-	 * @return a time_t value (expressed as a 64-bit number) or nullopt
+	 * @return a Date pair or nullopt
 	 */
 	Option<Date> date() const noexcept;
 
+	/**
+	 * Gets a { date, utc-offset } pair from the first (more recent)
+	 * Received: header, or nullopt if there is none.
+	 *
+	 * @return a Date pair or nullopt
+	 */
+	Option<Date> received() const noexcept;
 
 	/**
 	 * Get the references for this message (including in-reply-to), in the

lib/tests/test-mu-msg.cc

@@ -368,6 +368,31 @@ k+ZGGoQ0v8b7RwmyskMAAAAAAAAAAAAA
 }
 
 
+static void
+test_mu_msg_received_date()
+{
+	/* without a Date: header, fall back to the date in the topmost (most
+	 * recent) Received: header */
+	const auto txt =
+R"(Return-Path: me@example.com
+Received: from imap.example.com [61.223.64.18]
+	by evergrey with IMAP (fetchmail-6.6.6)
+	for <me@localhost> (single-drop); Thu, 30 Jul 2026 13:47:56 +0300 (EEST)
+Received: from mail.example.com ([10.11.12.13]);
+	Wed, 29 Jul 2026 01:02:03 +0000
+From: Me <me@example.com>
+To: You <you@example.com>
+Subject: no date
+Message-ID: <abcdef@example.com>
+
+Test.
+)";
+	const auto msg{Message::make_from_text(txt, "boo/cur/msg3:2,S")};
+	assert_valid_result(msg);
+
+	g_assert_cmpuint(msg->date(), ==, 1785408476); /* 2026-07-30 10:47:56 UTC */
+}
+
 [[maybe_unused]] static gboolean
 ignore_error(const char* log_domain, GLogLevelFlags log_level, const gchar* msg, gpointer user_data)
 {
@@ -402,6 +427,7 @@ main(int argc, char* argv[])
 	g_test_add_func("/msg/mu-msg-comp-unix-programmer", test_mu_msg_comp_unix_programmer);
 
 	g_test_add_func("/msg/mu-smime", test_mu_smime);
+	g_test_add_func("/msg/mu-msg-received-date", test_mu_msg_received_date);
 
 	g_test_add_func("/str/mu-str-prio-01", test_mu_str_prio_01);