Description:

The Java TNEF package is an open source code implementation of a TNEF message
handler, which can be used as a command-line utility or integrated into Java-
based mail applications to extract the original message content.

Transport-Neutral Encapsulation Format (TNEF) is Microsoft's non-standard
format for encapsulating mail which has any non-plain-text content or
properties (such as rich text, embedded OLE objects, voting buttons, and
sometimes just attachments). Whether or not a given message is encoded using
TNEF is determined by the Outlook default settings, per-recipient setting,
Exchange Server settings, and message type and content.

Once a TNEF message is used, the entire message, including all the original
attachments and properties, is encapsulated in a single attachment of mime
type "application/ms-tnef" added to the message to be sent over the Internet.
This attachment is usually named "WINMAIL.DAT", and when sent to any non-MS
mail client, is useless, and makes access to the original message attachments
impossible.