lib-sieve: vacation extension: Use Microsoft X-Auto-Response-Suppress header...

lib-sieve: vacation extension: Use Microsoft X-Auto-Response-Suppress header to prevent unwanted responses.

We've seen a few situations where Pigeonhole and Microsoft products start a useless machine conversation.
At least older versions of Outlook ignore the standards on multiple points to make this happen.
We prevent this now by recognizing and generating the X-Auto-Response-Suppress header.

src/lib-sieve/plugins/vacation/cmd-vacation.c

@@ -982,6 +982,9 @@ static int act_vacation_send
 	rfc2822_header_write(msg, "Auto-Submitted", "auto-replied (vacation)");
 	rfc2822_header_write(msg, "Precedence", "bulk");
 
+	/* Prevent older Microsoft products from replying to this message */
+	rfc2822_header_write(msg, "X-Auto-Response-Suppress", "All");
+
 	rfc2822_header_write(msg, "MIME-Version", "1.0");
 
 	if ( !ctx->mime ) {
@@ -1158,6 +1161,32 @@ static int act_vacation_commit
 		hdsp++;
 	}
 
+	/* Check for the (non-standard) Microsoft X-Auto-Response-Suppress header */
+	if ( mail_get_headers
+		(mail, "x-auto-response-suppress", &headers) < 0 ) {
+		return sieve_result_mail_error(aenv, mail,
+			"vacation action: "
+			"failed to read header field `x-auto-response-suppress'");
+	}
+	/* Theoretically multiple headers could exist, so lets make sure */
+	hdsp = headers;
+	while ( *hdsp != NULL ) {
+		const char *const *flags = t_strsplit(*hdsp, ",");
+		while ( *flags != NULL ) {
+			const char *flag = t_str_trim(*flags, " \t");
+			if ( strcasecmp(flag, "All") == 0 ||
+				strcasecmp(flag, "OOF") == 0 ) {
+				sieve_result_global_log(aenv,
+					"discarding vacation response to message from <%s> "
+					"(`%s' flag found in x-auto-response-suppress header)",
+					str_sanitize(sender, 128), flag);
+					return SIEVE_EXEC_OK;
+			}
+			flags++;
+		}
+		hdsp++;
+	}
+
 	/* Do not reply to system addresses */
 	if ( _is_system_address(sender) ) {
 		sieve_result_global_log(aenv,

tests/extensions/vacation/reply.svtest

@@ -146,6 +146,99 @@ test "No reply to auto-submitted mail" {
 	}
 }
 
+/*
+ * No reply to Microsoft X-Auto-Response-Suppress - All
+ */
+
+test_result_reset;
+
+test_set "message" text:
+From: spam@example.com
+To: stephan@example.com
+X-Auto-Response-Suppress: All
+Subject: Frop!
+
+Frop!
+.
+;
+
+test_set "envelope.from" "spam@example.com";
+test_set "envelope.to" "stephan@example.com";
+
+test "No reply to Microsoft X-Auto-Response-Suppress - All" {
+	vacation "I am gone";
+
+	if not test_result_execute {
+		test_fail "failed to execute vacation";
+	}
+
+	if test_message :smtp 0 {
+		test_fail "vacation not supposed to send message";
+	}
+}
+
+/*
+ * No reply to Microsoft X-Auto-Response-Suppress - OOF
+ */
+
+test_result_reset;
+
+test_set "message" text:
+From: spam@example.com
+To: stephan@example.com
+X-Auto-Response-Suppress: OOF
+Subject: Frop!
+
+Frop!
+.
+;
+
+test_set "envelope.from" "spam@example.com";
+test_set "envelope.to" "stephan@example.com";
+
+test "No reply to Microsoft X-Auto-Response-Suppress - OOF" {
+	vacation "I am gone";
+
+	if not test_result_execute {
+		test_fail "failed to execute vacation";
+	}
+
+	if test_message :smtp 0 {
+		test_fail "vacation not supposed to send message";
+	}
+}
+
+/*
+ * No reply to Microsoft X-Auto-Response-Suppress - DR,OOF,RN
+ */
+
+test_result_reset;
+
+test_set "message" text:
+From: spam@example.com
+To: stephan@example.com
+X-Auto-Response-Suppress: DR, OOF,	RN
+Subject: Frop!
+
+Frop!
+.
+;
+
+test_set "envelope.from" "spam@example.com";
+test_set "envelope.to" "stephan@example.com";
+
+test "No reply to Microsoft X-Auto-Response-Suppress - DR,OOF,RN" {
+	vacation "I am gone";
+
+	if not test_result_execute {
+		test_fail "failed to execute vacation";
+	}
+
+	if test_message :smtp 0 {
+		test_fail "vacation not supposed to send message";
+	}
+}
+
 /*
  * No reply to system address
  */
@@ -252,6 +345,7 @@ To: stephan@example.com
 Subject: Frop!
 Auto-submitted: no
 Precedence: normal
+X-Auto-Response-Suppress: None
 
 Frop!
 .