diff --git a/ChangeLog b/ChangeLog
index c60583dfe..b61f8754d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2011-08-10  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
+
+	* OpenChange/MAPIStoreMapping.m
+	(+mappingForUsername:withIndexing:): modified contrusctor to make
+	use of a "username" parameter that enable per-user "singletons".
+	(-increateUseCount, -decreaseUseCount): new accessors that enable
+	the registration/unregistration of the mapping object from the
+	singleton registry.
+
 2011-08-08  Wolfgang Sourdeau  <wsourdeau@inverse.ca>
 
 	* OpenChange/MAPIStoreFolder.m (-lookupMessage:): set the WOContext
diff --git a/OpenChange/MAPIStoreMapping.h b/OpenChange/MAPIStoreMapping.h
index d0e6c95ed..a6de24880 100644
--- a/OpenChange/MAPIStoreMapping.h
+++ b/OpenChange/MAPIStoreMapping.h
@@ -30,14 +30,22 @@
 
 @interface MAPIStoreMapping : NSObject
 {
+  NSString *username;
+  struct tdb_wrap *indexing;
   NSMutableDictionary *mapping; /* FID/MID -> url */
   NSMutableDictionary *reverseMapping; /* url -> FID/MID */
-  struct tdb_wrap *indexing;
+  NSUInteger useCount;
 }
 
-+ (id) mappingWithIndexing: (struct tdb_wrap *) indexing;
++ (id) mappingForUsername: (NSString *) username
+             withIndexing: (struct tdb_wrap *) indexing;
 
-- (id) initWithIndexing: (struct tdb_wrap *) indexing;
+- (id) initForUsername: (NSString *) username
+          withIndexing: (struct tdb_wrap *) indexing;
+
+
+- (void) increaseUseCount;
+- (void) decreaseUseCount;
 
 - (NSString *) urlFromID: (uint64_t) idKey;
 
diff --git a/OpenChange/MAPIStoreMapping.m b/OpenChange/MAPIStoreMapping.m
index ea8e0d94e..63ae6f83a 100644
--- a/OpenChange/MAPIStoreMapping.m
+++ b/OpenChange/MAPIStoreMapping.m
@@ -38,8 +38,15 @@
 #include <tdb.h>
 #include <tdb_wrap.h>
 
+static NSMutableDictionary *mappingRegistry = nil;
+
 @implementation MAPIStoreMapping
 
++ (void) initialize
+{
+  mappingRegistry = [NSMutableDictionary new];
+}
+
 static int
 MAPIStoreMappingTDBTraverse (TDB_CONTEXT *ctx, TDB_DATA data1, TDB_DATA data2,
 			     void *data)
@@ -67,14 +74,20 @@ MAPIStoreMappingTDBTraverse (TDB_CONTEXT *ctx, TDB_DATA data1, TDB_DATA data2,
   return 0;
 }
 
-+ (id) mappingWithIndexing: (struct tdb_wrap *) indexing
++ (id) mappingForUsername: (NSString *) username
+             withIndexing: (struct tdb_wrap *) indexing
 {
-  id newMapping;
+  id mapping;
 
-  newMapping = [[self alloc] initWithIndexing: indexing];
-  [newMapping autorelease];
+  mapping = [mappingRegistry objectForKey: username];
+  if (!mapping)
+    {
+      mapping = [[self alloc] initForUsername: username
+                                 withIndexing: indexing];
+      [mapping autorelease];
+    }
 
-  return newMapping;
+  return mapping;
 }
 
 - (id) init
@@ -84,12 +97,34 @@ MAPIStoreMappingTDBTraverse (TDB_CONTEXT *ctx, TDB_DATA data1, TDB_DATA data2,
       mapping = [NSMutableDictionary new];
       reverseMapping = [NSMutableDictionary new];
       indexing = NULL;
+      useCount = 0;
     }
 
   return self;
 }
 
-- (id) initWithIndexing: (struct tdb_wrap *) newIndexing
+- (void) increaseUseCount
+{
+  if (useCount == 0)
+    {
+      [mappingRegistry setObject: self forKey: username];
+      [self logWithFormat: @"mapping registered (%@)", username];
+    }
+  useCount++;
+}
+
+- (void) decreaseUseCount
+{
+  useCount--;
+  if (useCount == 0)
+    {
+      [mappingRegistry removeObjectForKey: username];
+      [self logWithFormat: @"mapping deregistered (%@)", username];
+    }
+}
+
+- (id) initForUsername: (NSString *) newUsername
+          withIndexing: (struct tdb_wrap *) newIndexing
 {
   NSNumber *idNbr;
   NSString *uri;
@@ -98,6 +133,7 @@ MAPIStoreMappingTDBTraverse (TDB_CONTEXT *ctx, TDB_DATA data1, TDB_DATA data2,
 
   if ((self = [self init]))
     {
+      ASSIGN (username, newUsername);
       indexing = newIndexing;
       tdb_traverse_read (indexing->tdb, MAPIStoreMappingTDBTraverse, mapping);
       keys = [mapping allKeys];
@@ -116,6 +152,7 @@ MAPIStoreMappingTDBTraverse (TDB_CONTEXT *ctx, TDB_DATA data1, TDB_DATA data2,
 
 - (void) dealloc
 {
+  [username release];
   [mapping release];
   [reverseMapping release];
   [super dealloc];