libytnef0-dev binary package in Ubuntu Precise amd64

 Yerase's TNEF Stream Reader allows you to decode application/ms-tnef
 e-mail attachments, which are usually entitled "winmail.dat" and are
 generally a file container format that is only readable by Microsoft
 Outlook. Some TNEF streams also include RTF-formatted data.
 .
 libytnef0 is the support library that exposes these functions to other
 programs. The ytnef program (and eponymous package) is the frontend for
 this library, so you should probably install that if you want to take
 advantage of it.
 .
 These are the development headers for libytnef0.

Source package