Slack, notices as direct messages
Above the tabs of Organization → Notifications, and only for Owners and Primary Owners, is the Slack block: Connect Slack, or Connected to ‹your Slack› with Disconnect.
An Owner connects the company’s Slack once and each person’s notices start going by direct message from the Nouter app; if the person isn’t in that Slack, they keep coming by email. It covers join requests, the daily summary and the email to admins when the custom domain goes down or comes back.
More in Notifications.