PidTagAttachLongFilename Canonical Property

Applies to: Outlook 2013 | Outlook 2016

Contains an attachment's long filename and extension, excluding path.

Associated properties:
Data type:
Message attachment


These properties pertain to the ATTACH_BY_VALUE, ATTACH_BY_REFERENCE, ATTACH_BY_REF_RESOLVE, and ATTACH_BY_REF_ONLY values of the PR_ATTACH_METHOD (PidTagAttachMethod) property. Platforms that support long filenames should set both the PR_ATTACH_LONG_FILENAME and PR_ATTACH_FILENAME (PidTagAttachFilename) properties when sending, and should check PR_ATTACH_LONG_FILENAME first when receiving.

The client application should set this property to a suggested long filename to be used if the host computer receiving a message supports long filenames. PR_ATTACH_LONG_FILENAME can be used as a filename for saving the attachment, and to supply the filename extension if the PR_ATTACH_EXTENSION (PidTagAttachExtension) property is not provided.

Unlike the filename provided by PR_ATTACH_FILENAME, this name is not restricted to an eight-character filename plus a three-character extension. Instead, it can be up to 256 characters long, including the filename, extension, and separator period.

MAPI works only with filenames in the ANSI character set. Client applications that use filenames in an OEM character set must convert them to ANSI before calling MAPI.

Protocol specifications


Handles message and attachment objects.


Converts from Internet standard email conventions to message objects.


Specifies the properties of rights-managed encoded messages.


Specifies the properties and operations that are permissible for representing voice mail and fax messages.

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