It might be a little late; but I would advise you to let http://uptime.openacs.org/uptime/ check your page for "uptime"; it checks if theres the word "Success" on the page ever 2 hours; else it'll email you. (So you'll have to add the word "Success" somewhere on your page and then every 2 hours your page will be visited and thus your cron might get just the push it needs to send mail on time.