Patch by Robert Scheck <robert@fedoraproject.org> for Zarafa >= 7.1.11 which adds anti-loop headers
for automatic responses by zarafa-autorespond for Microsoft Exchange and all vacation(1) compatible
implementations.

For the Microsoft Exchange related part useful links are:
 - http://msdn.microsoft.com/en-us/library/ee219609(v=exchg.80).aspx
 - https://www.jitbit.com/maxblog/18-detecting-outlook-autoreplyout-of-office-emails-and-x-auto-response-suppress-header/

For vacation(1) compatible implementations useful links are:
 - http://www.daemon-systems.org/man/vacation.1.html
 - Book "sendmail" (written by Bryan Costales, Claus Assmann, George Jansen, Gregory Neil Shapiro), ISBN 0596555342

Proposed to upstream via e-mail on Wed, 27 Aug 2014 23:59:58 +0200, patch was put into the upstream
ticket https://jira.zarafa.com/browse/ZCP-12591.

--- zarafa-7.1.11/spooler/DAgent.cpp				2014-08-24 12:27:06.000000000 +0200
+++ zarafa-7.1.11/spooler/DAgent.cpp.vacation-headers2		2014-08-27 23:52:42.000000000 +0200
@@ -1469,12 +1469,25 @@
 	if (hr != hrSuccess)
 		goto exit;
 
-	// add anti-loop header
+	// add anti-loop header for Zarafa
 	snprintf(szHeader, PATH_MAX, "\nX-Zarafa-Vacation: autorespond");
 	hr = WriteOrLogError(fd, szHeader, strlen(szHeader));
 	if (hr != hrSuccess)
 		goto exit;
 
+	// add anti-loop header for Exchange, see http://msdn.microsoft.com/en-us/library/ee219609(v=exchg.80).aspx
+	snprintf(szHeader, PATH_MAX, "\nX-Auto-Response-Suppress: All");
+	hr = WriteOrLogError(fd, szHeader, strlen(szHeader));
+	if (hr != hrSuccess)
+		goto exit;
+
+	// add anti-loop header for vacation(1) compatible implementations, see section 10.9 of book "sendmail" (written
+	// by Bryan Costales, Claus Assmann, George Jansen, Gregory Neil Shapiro), ISBN 0596555342
+	snprintf(szHeader, PATH_MAX, "\nPrecedence: bulk");
+	hr = WriteOrLogError(fd, szHeader, strlen(szHeader));
+	if (hr != hrSuccess)
+		goto exit;
+
 	if (lpMessageProps[3].ulPropTag == PR_SUBJECT_W) {
 		// convert as one string because of [] characters
 		swprintf(szwHeader, PATH_MAX, L"%ls [%ls]", szSubject, lpMessageProps[3].Value.lpszW);