User email are masked in Sandboxes and we can mask Contact emails as part of the data deployment. This still leaves the Org Wide addresses as valid emails. If there is automation that is generating emails related to the data that is loaded, they will be delivered to the Org Wide Addresses.

It would be useful if the same script that is deactivating validation rules could set email deliverability to systems emails at the same time.

In the even that email deliverability was set to all emails in the Sandbox and not adjusted before the data deployment we would have an extra safety net to prevent emails from going out.