/usr/bin/mh/sendfiles is in nmh 1.5-release-5.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 | #!/bin/sh
#
# Send multiples files and/or directories as a tar/compressed
# image, in a MIME message.
#
DELAY=0
FROM=
# compression method (none, gzip or compress)
METHOD=none
# compression filter
COMPRESS=cat
# uncompression filter
UNCOMPRESS=cat
# compression description to append to content-type
CONVERSION=
# default compression method based on installed software
# prefer compress over gzip for backward compatibility
if command -v compress >/dev/null 2>&1 ; then
    METHOD=compress
elif command -v gzip >/dev/null 2>&1 ; then
    METHOD=gzip
fi
# handle command-line options to override compression method and delay
while [ $# -gt 3 ]; do
    case "$1" in
        -gzip) METHOD=gzip
	       shift
	       ;;
	-compress) METHOD=compress
	           shift
		   ;;
        -none) METHOD=none
	       shift
	       ;;
	-*) DELAY="`echo $1 | sed -e 's%-%%'`"
	    shift
	    ;;
	*) break
	   ;;
    esac
done
# set variables based on chosen compression method
if [ $METHOD = compress ]; then
    COMPRESS=compress
    UNCOMPRESS=uncompress
    CONVERSION="; x-conversions=compress"
elif [ $METHOD = gzip ]; then
    COMPRESS="gzip -c"
    UNCOMPRESS="gzip -dc"
    CONVERSION="; x-conversions=gzip"
fi
if [ ! -z "$PERSON" ]; then
    FROM="-from $PERSON"
fi
if [ $# -lt 3 ]; then
    echo 'usage: sendfiles: "mailpath" "subject-string" directory-or-file ...' 1>&2
    exit 1;
fi
mailpath="$1"
echo "mailpath = $mailpath" 1>&2
shift
subject="$1"
echo "subject-string = $subject" 1>&2
shift
echo "files = $*" 1>&2
tar cvf - "$@" | $COMPRESS | \
    /usr/lib/mh/viamail -to "$mailpath" -subject "$subject" \
	-parameters "type=tar$CONVERSION" \
	-comment "extract with $UNCOMPRESS | tar xvpf -" \
	-delay "$DELAY" \
	-verbose $FROM
 |