Soon anyone from any company can Slack you

Slack will soon let anyone DM each other. A new Slack Connect direct messages feature will launch for businesses in early 2021 that expands on the idea of shared channels, and allows employees to directly connect with people from other organizations. If you’re a Slack Connect user, you’ll be able to share a private link with other Slack users to direct message you.
Slack has been building towards this ease of messaging between businesses for months. Slack Connect launched back in Jun