diff --git a/include/mapidefs.h b/include/mapidefs.h
index 27444275137..31ebf43b1ee 100644
--- a/include/mapidefs.h
+++ b/include/mapidefs.h
@@ -162,6 +162,7 @@ typedef struct _MAPIUID
 #define MAPI_ACCESS_CREATE_HIERARCHY  0x00000008U
 #define MAPI_ACCESS_CREATE_CONTENTS   0x00000010U
 #define MAPI_ACCESS_CREATE_ASSOCIATED 0x00000020U
+#define MAPI_USE_DEFAULT              0x00000040U
 #define MAPI_UNICODE                  0x80000000U /* Strings in this call are Unicode */
 
 #if defined (UNICODE) || defined (__WINESRC__)
@@ -170,6 +171,9 @@ typedef struct _MAPIUID
 #define fMapiUnicode 0U
 #endif
 
+/* IMAPISession::OpenMessageStore() flags */
+#define MDB_NO_DIALOG           0x00000001
+
 /* Types of message receivers */
 #ifndef MAPI_ORIG
 #define MAPI_ORIG      0          /* The original author */