I use elm on HP-UX - you have to run the elm command alone first if you have never used it. And then use an attach file that tells elm where the attachment is:
elm -s "Monthly Statistics" $EMAIL < /dci_wrk/attach.statistics
The attach file looks like this:
blank line
[include stats.csv text/plain]
My stats.csv file happens to be in the same directory as the attach file - if not, I would have to provide the path.