Metamail is a package of programs for handling MIME mail. The metamail distribution may be obtained by any of the methods described in the Section Obtaining Example Files From This Book. In the USA, it's available at ftp://ftp.research.telcordia.com/pub/nsb/mm2.7.tar.Z. In Europe, try ftp://ftp.funet.fi/pub/unix/mail/metamail/mm2.7.tar.Z.
On 21 May 1997, a CERT advisory was released on security problems in Metamail version 2.7. See the workarounds in the advisory.