Discourse has a setting to disable all outgoing emails.
If you enable this option Discourse shows an alert to let admins know and it looks like this when an you use an admin account:
However, the alert is also displayed to logged out users - and I presume to non-admin users as well - like so:
Logged out view:
Notice how the bootstrap alert does not show for logged out users. I expect the desired result is the same.
Edgy… but came across it so figured I should mention it