diff -r 2a9df0617cfb src/imap/imap-fetch.c
--- a/src/imap/imap-fetch.c	Thu Mar 13 15:55:19 2008 +0200
+++ b/src/imap/imap-fetch.c	Thu Mar 13 15:55:44 2008 +0200
@@ -9,6 +9,7 @@
 #include "message-send.h"
 #include "message-size.h"
 #include "imap-date.h"
+#include "imap-quote.h"
 #include "commands.h"
 #include "imap-fetch.h"
 #include "imap-util.h"
@@ -20,7 +21,7 @@
 #define ENVELOPE_NIL_REPLY \
 	"(NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL)"
 
-const struct imap_fetch_handler default_handlers[8];
+const struct imap_fetch_handler default_handlers[9];
 static buffer_t *fetch_handlers = NULL;
 
 static int imap_fetch_handler_cmp(const void *p1, const void *p2)
@@ -600,7 +601,28 @@ fetch_uid_init(struct imap_fetch_context
 	return TRUE;
 }
 
-const struct imap_fetch_handler default_handlers[8] = {
+static int fetch_guid(struct imap_fetch_context *ctx, struct mail *mail,
+		      void *context ATTR_UNUSED)
+{
+	const char *value;
+
+	if (mail_get_special(mail, MAIL_FETCH_UIDL_FILE_NAME, &value) < 0)
+		return -1;
+
+	str_append(ctx->cur_str, "X-GUID ");
+	imap_quote_append_string(ctx->cur_str, value, FALSE);
+	return 1;
+}
+
+static bool
+fetch_guid_init(struct imap_fetch_context *ctx ATTR_UNUSED, const char *name,
+		const struct imap_arg **args ATTR_UNUSED)
+{
+	imap_fetch_add_handler(ctx, TRUE, FALSE, name, "", fetch_guid, NULL);
+	return TRUE;
+}
+
+const struct imap_fetch_handler default_handlers[9] = {
 	{ "BODY", fetch_body_init },
 	{ "BODYSTRUCTURE", fetch_bodystructure_init },
 	{ "ENVELOPE", fetch_envelope_init },
@@ -608,5 +630,6 @@ const struct imap_fetch_handler default_
 	{ "INTERNALDATE", fetch_internaldate_init },
 	{ "MODSEQ", fetch_modseq_init },
 	{ "RFC822", fetch_rfc822_init },
-	{ "UID", fetch_uid_init }
+	{ "UID", fetch_uid_init },
+	{ "X-GUID", fetch_guid_init }
 };
diff -r 2a9df0617cfb src/imap/imap-search.c
--- a/src/imap/imap-search.c	Thu Mar 13 15:55:19 2008 +0200
+++ b/src/imap/imap-search.c	Thu Mar 13 15:55:44 2008 +0200
@@ -605,6 +605,9 @@ static bool search_arg_build(struct sear
 				return ARG_NEW_SINGLE(SEARCH_ALL);
 			}
 			return ARG_NEW_STR(SEARCH_TEXT_FAST);
+		} else if (strcmp(str, "X-GUID") == 0) {
+			/* <string> */
+			return ARG_NEW_STR(SEARCH_GUID);
 		}
 		break;
 	default:
diff -r 2a9df0617cfb src/lib-storage/index/index-search.c
--- a/src/lib-storage/index/index-search.c	Thu Mar 13 15:55:19 2008 +0200
+++ b/src/lib-storage/index/index-search.c	Thu Mar 13 15:55:44 2008 +0200
@@ -204,6 +204,7 @@ static int search_arg_match_cached(struc
 static int search_arg_match_cached(struct index_search_context *ctx,
 				   struct mail_search_arg *arg)
 {
+	const char *str;
 	struct tm *tm;
 	uoff_t virtual_size;
 	time_t date;
@@ -267,6 +268,11 @@ static int search_arg_match_cached(struc
 		else
 			return virtual_size > arg->value.size;
 
+	case SEARCH_GUID:
+		if (mail_get_special(ctx->mail, MAIL_FETCH_UIDL_FILE_NAME,
+				     &str) < 0)
+			return -1;
+		return strcmp(str, arg->value.str) == 0;
 	default:
 		return -1;
 	}
diff -r 2a9df0617cfb src/lib-storage/mail-search.h
--- a/src/lib-storage/mail-search.h	Thu Mar 13 15:55:19 2008 +0200
+++ b/src/lib-storage/mail-search.h	Thu Mar 13 15:55:44 2008 +0200
@@ -39,7 +39,8 @@ enum mail_search_arg_type {
 	SEARCH_TEXT_FAST,
 
 	/* extensions */
-	SEARCH_MODSEQ
+	SEARCH_MODSEQ,
+	SEARCH_GUID
 };
 
 enum mail_search_modseq_type {