diff --git a/ChangeLog b/ChangeLog
index cfa955fa6..31b1f9ec3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -23,6 +23,13 @@
 	limited perform a SOAP request to a MS Exhange server to retrieve
 	the freebusy information of a user.
 
+	* UI/Scheduler/UIxComponentEditor.m (-_loadAttendees): when the
+	attendee's email address doesn't match a user from the
+	authentication source(s), perform a lookup in the addressbook
+	source(s). If the email matches a user from a source with a
+	MSExchangeHostname, return a concatenation of the active user uid
+	and this contact uid.
+
 	* UI/WebServerResources/UIxAttendeesEditor.js
 	(performSearchCallback): if a matching contact has the
 	"isMSExchange" attribute, prefix the uid with the login uid.
diff --git a/SoObjects/Contacts/SOGoContactSourceFolder.m b/SoObjects/Contacts/SOGoContactSourceFolder.m
index cc25d0d76..16346f935 100644
--- a/SoObjects/Contacts/SOGoContactSourceFolder.m
+++ b/SoObjects/Contacts/SOGoContactSourceFolder.m
@@ -24,6 +24,7 @@
 #import <Foundation/NSDictionary.h>
 #import <Foundation/NSEnumerator.h>
 #import <Foundation/NSString.h>
+#import <Foundation/NSValue.h>
 
 #import <NGObjWeb/NSException+HTTP.h>
 #import <NGObjWeb/WOApplication.h>
@@ -160,6 +161,7 @@
 {
   NSMutableDictionary *newRecord;
   NSString *data;
+  NSObject <SOGoSource> *recordSource;
 
   newRecord = [NSMutableDictionary dictionaryWithCapacity: 8];
   [newRecord setObject: [oldRecord objectForKey: @"c_uid"]
@@ -218,6 +220,11 @@
   if ([data length] > 0)
     [newRecord setObject: data forKey: @"contactInfo"];
 
+  recordSource = [oldRecord objectForKey: @"source"];
+  if ([recordSource conformsToProtocol: @protocol (SOGoDNSource)] &&
+      [[(NSObject <SOGoDNSource>*) recordSource MSExchangeHostname] length])
+    [newRecord setObject: [NSNumber numberWithInt: 1] forKey: @"isMSExchange"];
+  
   return newRecord;
 }
 
diff --git a/UI/Scheduler/UIxComponentEditor.m b/UI/Scheduler/UIxComponentEditor.m
index 662eaa99e..c6841a5a4 100644
--- a/UI/Scheduler/UIxComponentEditor.m
+++ b/UI/Scheduler/UIxComponentEditor.m
@@ -61,6 +61,7 @@
 #import <SOGo/SOGoUser.h>
 #import <SOGo/SOGoUserDefaults.h>
 #import <SOGo/SOGoUserManager.h>
+#import <SOGo/SOGoSource.h>
 #import <SOGo/SOGoPermissions.h>
 #import <SOGo/SOGoSystemDefaults.h>
 #import <SOGo/WOResourceManager+SOGo.h>
@@ -248,9 +249,12 @@ iRANGE(2);
 {
   NSEnumerator *attendees;
   NSMutableDictionary *currentAttendeeData;
+  NSString *uid, *domain;
+  NSArray *contacts;
+  NSDictionary *contact;
   iCalPerson *currentAttendee;
-  NSString *uid;
   SOGoUserManager *um;
+  NSObject <SOGoSource> *source;
 
   jsonAttendees = [NSMutableDictionary new];
   um = [SOGoUserManager sharedUserManager];
@@ -271,6 +275,23 @@ iRANGE(2);
       if (uid != nil)
 	[currentAttendeeData setObject: uid 
 				forKey: @"uid"];
+      else
+        {
+          domain = [[context activeUser] domain];
+          contacts = [um fetchContactsMatching: [currentAttendee rfc822Email] inDomain: domain];
+          if ([contacts count] == 1)
+            {
+              contact = [contacts lastObject];
+              source = [contact objectForKey: @"source"];
+              if ([source conformsToProtocol: @protocol (SOGoDNSource)] &&
+                  [[(NSObject <SOGoDNSource>*) source MSExchangeHostname] length])
+                {
+                  uid = [NSString stringWithFormat: @"%@:%@", [[context activeUser] login],
+                              [contact valueForKey: @"c_uid"]];
+                  [currentAttendeeData setObject: uid forKey: @"uid"];
+                }
+            }
+        }
 
       [currentAttendeeData setObject: [[currentAttendee partStat] lowercaseString]
 			      forKey: @"partstat"];