PidTagAttachDataBinary Canonical Property

Applies to: Outlook 2013 | Outlook 2016

Contains binary attachment data typically accessed through the Object Linking and Embedding (OLE) IStream interface.

Associated properties:
Data type:
Message attachment


This property holds the attachment when the value of the PR_ATTACH_METHOD (PidTagAttachMethod) property is ATTACH_BY_VALUE, which is the usual attachment method and the only one required to be supported. PR_ATTACH_DATA_BIN also holds an OLE 1.0 OLESTREAM attachment when the value of PR_ATTACH_METHOD is ATTACH_OLE.

OLESTREAM attachments can be copied into a file by calling the OLE IStream::CopyTo method. The OLE encoding type can be determined from the PR_ATTACH_TAG (PidTagAttachTag) property.

For an OLE document file attachment, the message store provider must respond to an IMAPIProp::OpenProperty call on PR_ATTACH_DATA_OBJ (PidTagAttachDataObject) and may optionally respond to a call on PR_ATTACH_DATA_BIN. Note that PR_ATTACH_DATA_BIN and PR_ATTACH_DATA_OBJ share the same property identifier and thus are two renditions of the same property.

For a storage object, such as a compound file in OLE 2.0 docfile format, some service providers allow it to be opened with the MAPI IStreamDocfile interface for improved performance. A provider that supports IStreamDocfile must expose it on PR_ATTACH_DATA_OBJ and may optionally expose it on PR_ATTACH_DATA_BIN.

For more information on OLE interfaces and formats, see OLE and Data Transfer.

Protocol specifications


Handles message and attachment 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