Transport Neutral Encapsulation Format
Transport Neutral Encapsulation Format (TNEF) is a proprietary format used by Microsoft mail software to encode attachments and rich text, instead of more standards-compliant methods such as MIME.
It is usually implemented as an attachment called winmail.dat or win.dat, which Microsoft programs know what to do with, but is a useless and confusing attachment to everybody else (unless they use one of several programs and plugins that have been devised to help non-MS-ers cope with it). When saved elsewhere as archives or samples, sometimes the .tnef file extension is used.
Such mail files start with signature bytes
0x78 0x9f 0x3e 0x22.
- Fentun: Freeware Windows program to decode this attachment
- TNEF: An open source TNEF decoder utility
- Lookout: Thunderbird addon to read TNEF (based on the above TNEF decoder utility)
- Winmail Opener
- ytnef: TNEF command-line extractor