Comment # 5 on bug 919687 from Vitezslav Cizek

(In reply to Sebastian Freundt from comment #3)
> I'm particularly annoyed about the line in crontab(5):
> 
> In addition to LOGNAME, HOME, and SHELL, cron(8) looks at the MAILTO
> variable if a mail needs to be send as a result of running any commands in
> that particular crontab.

In cron(8) you can find:
"When executing commands, any output is mailed to the owner of the crontab"
I agree that this isn't documented very well.

However, this bug should rather be reported upstream at:
https://fedorahosted.org/cronie/