Noel, I did a quick look at that code.   That is some of it for sure - looks like the parts in /usr/bin and maybe some of /usr/lib (MH was scatter all of the file system in traditional UNIX manner -- lots of small programs - each to do one job only - each fit in a small address PDP-11 just fine).  The docs are missing and the MTA part is not there (which I think I remember was called 'submit' - but I could be very wrong on that).   It's the second version because that code is using stdio, the first version used a Rand IO library, if I remember right (not the portable C library).

Clem

PS For all you younger readers to this list, you need to remember that for early C, I/O was specifically not defined as part of the language (in some sense it is still not), so many early programs had their own libraries and its a good way to date things.   If the code is using stdio, it actually more 'modern' in the life of the PDP-11 [post 'typesetter C'].     BTW: I can say, in the mid 1970s, I personally found the lack of defined I/O confusing when I was learning the language and (remember Dennis has not yet written the 'White Book' which was really part of V7).   It was one of my bitches about C compared to BLISS, which was what I was coming and was a very rich system at CMU - while I/O in C was really a pain because ever program did it different - everybody wrote their own routines - which I thought was silly.   Soon there after the 'portable C library' appeared and then with typesetter C, stdio.