Ok, i'm just testing osticket for the moment, i made a mistake on my post, the system errors send a mail to the admin when my osticket can't fetch mail in the support mail.
I let my VM with OSticket off the network 3 days and when i restart network, it sent 500 mails to alert me that it can't fetch the mail.(i've setup cron every 3 minutes to fetch mail)
I think i can't configure my postfix to filter email and not send this alerts.
I understand This should not be disabled, but if i only can see the systems error on Osticket interface that enought for me, the sending mail fonction for systems error is not essential.