PidTagAttachFilename Canonical Property

Applies to: Outlook 2013 | Outlook 2016

Contains an attachment's base file name and extension, excluding path.

Associated properties:
Data type:
Message attachment


It is recommended that attachment objects expose these properties which 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. PR_ATTACH_FILENAME and associated properties are required when any of these values is used.

These properties can be used as a suggested file name for saving the attachment and to supply the file name extension if the PR_ATTACH_EXTENSION (PidTagAttachExtension) property is not provided.

The file name is restricted to eight characters plus a three-character extension. For a platform that supports long file names, set both this property and the PR_ATTACH_LONG_FILENAME (PidTagAttachLongFilename) property.

MAPI works only with file names, and other strings passed to it, in the American National Standards Institute (ANSI) character set. Client applications that use file names in an original equipment manufacturer (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 S/MIME signed and encrypted message properties.


Encodes and decodes message and attachment objects to an efficient stream representation.

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