NETSEND
NETSEND is a DOS utility that creates single-file self-extracting compressed archive files in COM format. It was developed by Jim Tucker. It is a spin-off of NETRUN.
The files it creates use an ASCII-only encoding suitable for inclusion in an email. See Executable envelopes#Transfer-encoded executables for other executable formats of this sort.
Discussion
The ASCII-encoded files are normally wrapped in some plain text instructions, telling you to use a text editor to save the payload data to a .COM file. There is a -z option to omit the wrapper, producing a file that can be executed directly (though you may have to rename it to end in ".COM").
Identification
Ignoring any wrapper, files begin with "XPPPYZIQD". This does not distinguish them from some NETPIC and NETRUN files.
Files made by v1.00 (the only version?) have "NETSEND_V1.00_JRT" at offset 46.
