Ah ... Makes sense.  MMDF was possibly my favorite Unix MTA.   We shipped it as Masscomp's default Mail System for a longtime.   It was only after I left that they broken down and switched to sendmail to be like Sun and much of the rest of the internet.

It's Interesting, MMDF had a child, PMDF (the rewrite in Pascal) which became the the default Mailer for a lot of VMS systems, particularly ones that had IP connections.  I know of no one still running MMDF at this point (even me), but I do know of a couple of folks running PMDF.  A few years ago, I gave up on MMDF and switched to Bornstien's QMAIL because of DNS issues.    In many ways, MMDF and QMAIL are a lot alike in the way they work under the covers, but to give Bornstien credit he had really walked through QMAIL doing a security audit and I was unwilling to take the time to do that for MMDF; and I knew that any MTA on the internet had to be hardenned.  I'm sure MMDF could be attacked with stack overwrites and strcpy(3) style attacks because when Crocker wrote it, that was not what was being considered.