I am writing an Outlook add-in in which I need to access custom attributes in a room (resource) mailbox. Through the Exchange management console, I have added custom attributes to a particiular room mailbox. When I run mfcmapi (the MAPI Editor) against my Exchange server, I can see the two attributes (properties) I added. For example the first one shows this information: Named Prop GUID: {48862A09-F786-0114-0283-000000000000} Property Name(s): PR_EMS_AB_EXTENSION_ATTRIBUTE_1, PR_EMS_AB_EXTENSION_ATTRIBUTE_1_A Type: PT_STRING8 Tag: 0x802D001E Named Prop Name ID: 65575=0x10027 Value: Attribute1 (a string) In my outlook add-in, I get an ExchangeUser (UserR) for this mailbox and I get the propertyaccessor: Outlook.PropertyAccessor pa = UserR.PropertyAccessor; I am able to retrieve all the built-in properties of this mailbox (for example the business telephone number) by using calls like: private const string BUSINESS_TELEPHONE_NUMBER http://schemas.microsoft.com/mapi/proptag/0x3A08001E string sBusPhone = (string) pa.GetProperty(BUSINESS_TELEPHONE); But I cannot seem to get the custom attributes. I cannot get them through their proptag because their tags are greater than 0x80000000. So, I am trying to retrieve them using this call: private const string CUSTOM_ATTRIBUTE_1 http://schemas.microsoft.com/mapi/string/ {48862A09-F786-0114-0283-000000000000}/PR_EMS_AB_EXTENSION_ATTRIBUTE_1 string sCustomAtt = (string) pa.GetProperty(CUSTOM_ATTRIBUTE_1); This call throws an exception. Does anyone know how to access these properties? Thanks, Mike
