No cron on mirror
The cron jobs give up-to-date information about whats happening on the mirror so IMO it's not a good idea not to have the cron jobs running.
Maybe there is something you could do with your email script which prevents the mirror from sending you mail.
If you still want to edit the cron jobs you can do this:
As root on the mirror
select your editor (<----- most likely "vim")
and you should see these 2 jobs:
* * * * * /usr/local/ispconfig/server/server.sh > /dev/null 2>> /var/log/ispconfig/cron.log
30 00 * * * /usr/local/ispconfig/server/cron_daily.sh > /dev/null 2>> /var/log/ispconfig/cron.log
You can comment them # to stop them from running.