diff -urB cyrus-imapd-2.4.6/imap/imapd.c cyrus-imapd-2.4.6-idle/imap/imapd.c
--- cyrus-imapd-2.4.6/imap/imapd.c	2010-12-20 13:15:49.000000000 +0000
+++ cyrus-imapd-2.4.6-idle/imap/imapd.c	2011-01-28 18:11:04.000000000 +0000
@@ -2674,8 +2674,31 @@
 	 * connection abort we tell idled about it */
 	idling = 1;
 
-	/* Get continuation data */
-	c = getword(imapd_in, &arg);
+        for (;;) {
+                /* Get continuation data */
+                c = getword(imapd_in, &arg);
+
+                if (!config_getswitch(IMAPOPT_OUTLOOK_IDLE_WORKAROUND))
+                        break;
+
+                /* has read some data */
+                if (c != EOF)
+                        break;
+
+                /* At this point we don't know :
+                 * - if we sent an unsolicited IMAP response
+                 * - if the timeout is reached
+                 *
+                 * Apply Outlook workaround in all case :
+                 * - send something on the wire to keep alive FW and IMAP client
+                 * - reset client timeout and wait again for end of command
+                 */
+                prot_printf(imapd_out, "* OK keep alive\r\n");
+                prot_flush(imapd_out);
+
+                prot_reset(imapd_in);
+                prot_resettimeout(imapd_in);
+        }
 
 	/* Stop updates and do any necessary cleanup */
 	idling = 0;
@@ -2732,6 +2755,18 @@
 	    /* If not running IDLE on backend, poll the mailbox for updates */
 	    if (!CAPA(backend_current, CAPA_IDLE)) {
 		imapd_check(NULL, 0);
+
+                /* Apply Outlook workaround.
+                 * Since the backend doesn't support idle,
+                   proxy must send keep alive by itself */
+                if (done && config_getswitch(IMAPOPT_OUTLOOK_IDLE_WORKAROUND)
+                                && prot_hasexpired(imapd_in)) {
+                        prot_printf(imapd_out, "* OK keep alive\r\n");
+                        prot_flush(imapd_out);
+
+                        prot_resettimeout(imapd_in);
+                        done = 0;
+                }
 	    }
 	}
 
diff -urB cyrus-imapd-2.4.6/lib/imapoptions cyrus-imapd-2.4.6-idle/lib/imapoptions
--- cyrus-imapd-2.4.6/lib/imapoptions	2010-12-20 13:15:49.000000000 +0000
+++ cyrus-imapd-2.4.6-idle/lib/imapoptions	2011-01-28 18:11:04.000000000 +0000
@@ -1310,6 +1310,9 @@
    interface, otherwise the user is assumed to be in the default
    domain (if set). */
 
+{ "outlook_idle_workaround", 0, SWITCH }
+/* See bug reported here for more details : http://www.washington.edu/imap/IMAP-FAQs/index.html#7.37 */
+
 /*
 .SH SEE ALSO
 .PP
diff -urB cyrus-imapd-2.4.6/lib/prot.c cyrus-imapd-2.4.6-idle/lib/prot.c
--- cyrus-imapd-2.4.6/lib/prot.c	2010-12-20 13:15:49.000000000 +0000
+++ cyrus-imapd-2.4.6-idle/lib/prot.c	2011-01-28 18:11:04.000000000 +0000
@@ -411,6 +411,17 @@
 }
 
 /*
+ * Check if timeout for the stream 's' has expired.
+ * 's' must have been created for reading.
+ */
+int prot_hasexpired(struct protstream *s)
+{
+        assert(!s->write);
+
+        return (s->timeout_mark - time(NULL)) <= 0;
+}
+
+/*
  * Set the stream 's' to flush the stream 'flushs' before
  * blocking for reading. 's' must have been created for reading,
  * 'flushs' for writing.
@@ -529,6 +540,15 @@
 }
 
 /*
+ * Permit to reuse the stream after an error
+ */
+void prot_reset(struct protstream *s)
+{
+        s->error = 0;
+        s->eof = 0;
+}
+
+/*
  * Read data into the empty buffer for the stream 's' and return the
  * first character.  Returns EOF on EOF or error.
  */
diff -urB cyrus-imapd-2.4.6/lib/prot.h cyrus-imapd-2.4.6-idle/lib/prot.h
--- cyrus-imapd-2.4.6/lib/prot.h	2010-12-20 13:15:49.000000000 +0000
+++ cyrus-imapd-2.4.6-idle/lib/prot.h	2011-01-28 18:11:04.000000000 +0000
@@ -216,6 +216,9 @@
 /* Reset the timeout timer for the connection (in seconds) */
 extern int prot_resettimeout(struct protstream *s);
 
+/* Check if the timeout has expired for the connection */
+extern int prot_hasexpired(struct protstream *s);
+
 /* Connect two streams so that when you block on reading s, the layer
  * will automaticly flush flushs */
 extern int prot_setflushonread(struct protstream *s,
@@ -233,6 +236,7 @@
 
 extern const char *prot_error(struct protstream *s);
 extern int prot_rewind(struct protstream *s);
+extern void prot_reset(struct protstream *s);
 
 /* Fill the buffer for a read stream with waiting data (may block) */
 extern int prot_fill(struct protstream *s);