Not anywhere in osticket....
Are they error messages generated by osticket, or by crond?
If they're generated by osticket, depending on your osticket's outbound mail configuration, it would either be in the sendmail queue or the smtp server queue. If they're generated by crond, it's most likely going through sendmail.
If you're on a shared host, those are probably not something you have access to. You might have something like a .Mail folder in your home directory. If so, look for an outbox...
Otherwise....
http://www.linuxquestions.org/questions/linux-software-2/sendmail-command-to-flush-queue-49694(http://www.linuxquestions.org/questions/linux-software-2/sendmail-command-to-flush-queue-49694)
If you're not using sendmail, clearing the smtp server queue varies depending on which smtpd you're using. Here are a couple...
POSTFIX: http://www.cyberciti.biz/tips/howto-postfix-flush-mail-queue.html(http://www.cyberciti.biz/tips/howto-postfix-flush-mail-queue.html)
Exim: http://www.cyberciti.biz/faq/exim-remove-all-messages-from-the-mail-queue(http://www.cyberciti.biz/faq/exim-remove-all-messages-from-the-mail-queue)
Exchange: http://www.virtualhelp.me/windows/53-clean-out-smtp-queue-in-ms-exchange(http://www.virtualhelp.me/windows/53-clean-out-smtp-queue-in-ms-exchange)