Transport-Neutral Encapsulation Format (TNEF)
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. ArchiveDisclaimer

Transport-Neutral Encapsulation Format (TNEF)

This content is outdated and is no longer being maintained.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.

TNEF is a format for converting a set of MAPI properties—a MAPI message—into a serial data stream. The TNEF functions are primarily used by transport providers that need to encode MAPI message properties for transmission through a messaging system that does not support those properties directly. For example, an SMTP-based transport uses TNEF to encode properties like PR_SENT_REPRESENTING_NAME (PidTagSentRepresentingName), which do not have direct representations in the structure of an SMTP message.

The TNEF implementation defines several TNEF-specific attributes, each of which corresponds to a particular MAPI property. These attributes are used to encode their respective MAPI properties into the TNEF stream. In addition, a special attribute is defined that can be used to encapsulate any MAPI property that does not have a specific attribute corresponding to it. The reason these attributes are defined — instead of simply using a uniform encoding method for all MAPI properties — is to enable backward compatibility with non-MAPI-compliant software that is using TNEF.

The remainder of this appendix describes the structure and syntax of a TNEF stream, the mapping between MAPI properties and TNEF attributes, and important considerations for certain TNEF attributes.

© 2015 Microsoft