PidTagContentUnreadCount Canonical Property

Applies to: Outlook 2013 | Outlook 2016

Contains the number of unread messages in a folder, as computed by the message store.

Associated properties:
Data type:


This property computed by the message store is used for two different, though related, purposes. On a MAPI folder object, it contains the number of messages in a folder. In a heading row in categorized MAPI tables, it contains the number of unread non-associated messages in the category corresponding to that heading row.

This property contains the number of messages in the folder contents table for which the MSGFLAG_READ flag is not set in the PR_MESSAGE_FLAGS (PidTagMessageFlags) property. The PR_CONTENT_COUNT (PidTagContentCount) property contains the total message count for the folder. The PR_CONTENT_COUNT and this property are read-only to clients.

Some client applications display the heading row of a category differently depending on the value of this property. For example, a client can display a category that includes unread messages in bold. This property cannot be used as a category and an attempt to do so results in the MAPI_E_INVALID_PARAMETER value being returned from the IMAPITable::SortTable method.

Protocol specifications


Provides references to related Microsoft Exchange Server protocol specifications.


Handles folder operations.


Includes permissible operations for the core table objects.

Header files


Provides data type definitions.


Contains definitions of properties listed as alternate names.

See also

MAPI Properties

MAPI Canonical Properties

Mapping Canonical Property Names to MAPI Names

Mapping MAPI Names to Canonical Property Names