The cron that's referenced in the email you forwarded that seems to have created this:
cd /home/aras/acis && nice -n 12 /home/aras/acis/bin/make-repec-per.sh
runs every hour and emails "
aras@repec.org". I see those emails as sent in the mail logs on the nebka server and on the mail relay that sends through AWS SES. It would seem that you should be getting a lot of emails.
I'm not sure what to do with this. If this is the only one you've seen, maybe we wait and see if another one ever gets sent to you, and see if that provides more information?