Every time the administrator restores a backup, this always appears: Outgoing email has been disabled for non-staff users
(But it was set to: disable emails:NO)
This is intentional. I suppose, to prevent users to be spammed with unintended mails when restoring a backup to a staging site.
You have to change the config option disable emails by hand.
Except for updating a staged site, can one assume that the frequency of restores is rare?
For cases of automatic restores, such as when synchronizing a staging instance, these configuration values can also be set via a script.
This is a fantastic feature. The likelihood that you don’t want to send emails to every single person in your database after you restore a backup without at least checking on a thing or two is very, very high.
If you mean that was the value before restored the backup then that is what is expected.