Index: imap/imapd.c
===================================================================
RCS file: /cvs/src/cyrus/imap/imapd.c,v
retrieving revision 1.510
diff -u -r1.510 imapd.c
--- imap/imapd.c	13 Feb 2007 17:04:27 -0000	1.510
+++ imap/imapd.c	14 Feb 2007 14:52:45 -0000
@@ -4006,16 +4006,22 @@
 			imapd_mailbox->highestmodseq);
     }
 
-    if (usinguid || config_getswitch(IMAPOPT_FLUSHSEENSTATE)) {
-	if (usinguid) fetchitems |= FETCH_UID; 
-	index_check(imapd_mailbox, usinguid, /* update \Seen state from disk? */
-		    config_getswitch(IMAPOPT_FLUSHSEENSTATE) << 1 /* quiet */);
+    /* EXPUNGE responses allowed for UID FETCH */
+    if (usinguid) {
+	fetchitems |= FETCH_UID;
+	index_check(imapd_mailbox, 1, 0);
     }
 
     fetchargs.fetchitems = fetchitems;
     r = index_fetch(imapd_mailbox, sequence, usinguid, &fetchargs,
 		&fetchedsomething);
 
+    if (config_getswitch(IMAPOPT_FLUSHSEENSTATE)) {
+        /* Flush \Seen state to disk immediately (but only if anything
+           changed) and check for updates by other processes */
+        index_check_existing(imapd_mailbox, usinguid, 1);  
+    }
+
     snprintf(mytime, sizeof(mytime), "%2.3f", 
 	     (clock() - start) / (double) CLOCKS_PER_SEC);
 
@@ -4025,11 +4031,6 @@
     } else if (fetchedsomething || usinguid) {
 	prot_printf(imapd_out, "%s OK %s (%s sec)\r\n", tag,
 		    error_message(IMAP_OK_COMPLETED), mytime);
-	if (config_getswitch(IMAPOPT_FLUSHSEENSTATE) &&
-	    (fetchargs.fetchitems & FETCH_SETSEEN)) {
-	    /* flush \Seen state to disk */
-	    index_check(imapd_mailbox, usinguid, 2 /* quiet */);
-	}
     } else {
 	/* normal FETCH, nothing came back */
 	prot_printf(imapd_out, "%s NO %s (%s sec)\r\n", tag,
@@ -4157,9 +4158,11 @@
 
     index_fetch(imapd_mailbox, msgno, 0, &fetchargs, &fetchedsomething);
 
-    index_check(imapd_mailbox, 0,  /* flush \Seen state to disk? */
-		config_getswitch(IMAPOPT_FLUSHSEENSTATE) &&
-		fetchedsomething && (fetchargs.fetchitems & FETCH_SETSEEN));
+    if (config_getswitch(IMAPOPT_FLUSHSEENSTATE)) {
+        /* Flush \Seen state to disk immediately (but only if anything
+           changed) and check for updates by other processes */
+        index_check_existing(imapd_mailbox, 0, 1);
+    }
 
     if (fetchedsomething) {
 	prot_printf(imapd_out, "%s OK %s\r\n", tag,
@@ -4369,13 +4372,14 @@
     r = index_store(imapd_mailbox, sequence, usinguid, &storeargs,
 		    flag, nflags);
 
-    if (config_getswitch(IMAPOPT_FLUSHSEENSTATE) &&
-	(storeargs.seen || storeargs.operation == STORE_REPLACE)) {
-	/* flush \Seen state to disk */
-	index_check(imapd_mailbox, usinguid, 1);
-    }
-    else if (usinguid) {
-	index_check(imapd_mailbox, 1, 0);
+    if (usinguid) {
+        /* EXPUNGE responses allowed */
+	index_check(imapd_mailbox, 1, 1);   /* Check \Seen too */
+    } else if (config_getswitch(IMAPOPT_FLUSHSEENSTATE)) {
+        /* EXPUNGE responses not allowed */
+        /* Flush \Seen state to disk immediately (but only if anything
+           changed) and check for updates by other processes */
+        index_check_existing(imapd_mailbox, 0, 1);
     }
 
     if (r) {
Index: imap/imapd.h
===================================================================
RCS file: /cvs/src/cyrus/imap/imapd.h,v
retrieving revision 1.63
diff -u -r1.63 imapd.h
--- imap/imapd.h	30 Nov 2006 17:11:18 -0000	1.63
+++ imap/imapd.h	14 Feb 2007 14:52:45 -0000
@@ -241,6 +241,8 @@
 extern void index_operatemailbox(struct mailbox *mailbox);
 extern void index_check(struct mailbox *mailbox, int usinguid,
 			   int checkseen);
+extern void index_check_existing(struct mailbox *mailbox,
+                                 int usinguid, int checkseen);
 extern void index_checkseen(struct mailbox *mailbox, int quiet,
 			       int usinguid, int oldexists);
 
Index: imap/index.c
===================================================================
RCS file: /cvs/src/cyrus/imap/index.c,v
retrieving revision 1.223
diff -u -r1.223 index.c
--- imap/index.c	5 Feb 2007 18:41:46 -0000	1.223
+++ imap/index.c	14 Feb 2007 14:52:45 -0000
@@ -460,6 +460,54 @@
     }
 }
 
+/* Flush seen state (but only if anything changed) and check for flag/seen
+ * updates from other processes.  Bails out if the cyrus.index file has
+ * changed under our feet, which indicates an expunge from another process.
+ * In this case pending updates will be flushed on the next index_check()
+ */
+void
+index_check_existing(struct mailbox *mailbox, int usinguid, int checkseen)
+{
+    struct stat sbuf;
+    int msgno, i;
+    bit32 user_flags[MAX_USER_FLAGS/32];
+
+    if (imapd_exists == -1)
+        return;
+
+    /* Check for expunge, just like index_check() */
+    if (index_len) {
+        char fnamebuf[MAX_MAILBOX_PATH+1], *path;
+
+	path = (mailbox->mpath &&
+		(config_metapartition_files &
+		 IMAP_ENUM_METAPARTITION_FILES_INDEX)) ?
+	    mailbox->mpath : mailbox->path;
+	strlcpy(fnamebuf, path, sizeof(fnamebuf));
+	strlcat(fnamebuf, FNAME_INDEX, sizeof(fnamebuf));
+
+	if ((stat(fnamebuf, &sbuf) != 0) ||
+            (sbuf.st_ino != mailbox->index_ino) ||
+	    (index_ino != mailbox->index_ino))
+            return;
+    }
+
+    if (checkseen)
+        index_checkseen(mailbox, 0, usinguid, imapd_exists);
+
+    for (msgno = 1; msgno <= imapd_exists; msgno++) {
+	if (flagreport[msgno] < LAST_UPDATED(msgno)) {
+	    for (i = 0; i < VECTOR_SIZE(user_flags); i++) {
+		user_flags[i] = USER_FLAGS(msgno, i);
+	    }
+	    index_fetchflags(mailbox, msgno, SYSTEM_FLAGS(msgno), user_flags,
+			     LAST_UPDATED(msgno));
+	    if (usinguid) prot_printf(imapd_out, " UID %u", UID(msgno));
+	    prot_printf(imapd_out, ")\r\n");
+	}
+    }
+}
+
 /*
  * Checkpoint the user's \Seen state
  *