All outgoing email has been globally disabled by an administrator

Product Support
6

I have tired to restore from UI, and restore got failed, and I got message:

All outgoing email has been globally disabled by an administrator. No email notifications of any kind will be sent.

root@xxx-app:/var/www/discourse# rails c
[1] pry(main)> SiteSetting.disable_emails = false
Discourse::InvalidParameters: value
from /var/www/discourse/lib/site_settings/type_supervisor.rb:181:in `validate_value'
[2] pry(main)>

but it does not help,

please let me know, how to remove this message and enable notifications.
Thanks.

@Falco, please let me know how to remove message and enable notifications.