Does your email subject look like this?

@ryanhowson yes

If you access the page I previously mentioned while logged in to the sandbox, you'll be able to turn the emails off. Emails sent by the sandbox don't reach specific users and are re-routed based on the options you select.

but I want to terminate emails just for one user not for all

Just to confirm, you want emails generated by the sandbox to still reach users?

yes

Take a look at SuiteAnswers 20152, I haven't come across a situation where it's possible to send sandbox emails to users other than the logged in user, or the email that is defined as the send to email.

thanks