Sometimes things that run like clockwor does not when running via cron.
Especially, mails from cron tend not to work.
In hunting another such ghost problem, I optimized my 2-liner blocking the shell 60 seconds to a non-blocking one-liner:
echo '* * * * * root /bin/echo "test from cron" && rm /etc/cron.d/mailtest' >/etc/cron.d/mailtest
From: IBCL BLog.
Originally posted: 2009-02-06