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.

ytnef parses these streams into normal mime attachments and rtf attachments that you can read from non-outlook mail readers.

a convenience script is provided to allow users to transparently filter messages containing tnef attachments into messages with proper attachments, via procmail.