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Important This document may not represent best practices for current development, links to downloads and other resources may no longer be valid. Current recommended version can be found here.

PidTagAttachExtension Canonical Property

This content is outdated and is no longer being maintained. It is provided as a courtesy for individuals who are still using these technologies. This page may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist.

Contains a file name extension that indicates the document type of an attachment.

Associated properties:




Data type:



Message attachment

These properties are set by the client application at submission time.

The messaging system uses PR_ATTACH_EXTENSION when converting message attachments (in-route conversion) or launching applications based on attachments in received messages. If the sending client does not provide a value for these properties, the message store handling the attachment is not obligated to generate it. The receiving client should first check for PR_ATTACH_EXTENSION, and if it is not provided, should parse the file name extension from the attachment's PR_ATTACH_FILENAME (PidTagAttachFilename) or PR_ATTACH_LONG_FILENAME (PidTagAttachLongFilename) property.

Protocol Specifications


Handles message and attachment objects.

Header Files


Provides data type definitions.


Contains definitions of properties listed as alternate names.

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