By default, members (but not guests) can invite new members to your workspace. If you’d like, you can change this so that invitations must be requested and approved.
Note: When an invitation request is approved or denied, the member who requested it will be notified.
Manage invitation permissions
Use the steps below to manage whether workspace invitations must be approved.
From your desktop, click your workspace name in the sidebar.
Hover over Tools & settings, then select Workspace settings.
Click the Permissions tab.
Next to Invitations, click Expand.
Check or uncheck the box next to Require admin approval.
Click Save.
Manage where invitation requests are sent
When admin approval is required, you can choose where invitation requests are sent: to all admins via Slackbot, or to a specific channel.
From your desktop, click your workspace name in the sidebar.
Hover over Tools & settings, then select Workspace settings.
Click the Permissions tab.
Below Invitations, make sure the box next to Require admin approval is checked.
Choose whether requests will be sent to all admins or routed to a channel.
Click Save.
Manage invitation requests on Enterprise Grid with APIs
Using a set of APIs, Org Owners and Org Admins can build a custom app for Slack to manage invitation requests for workspaces in their Enterprise Grid organization. Apps built with these APIs can be connected to third-party services, like an identity provider (IDP) or IT ticketing software, to ensure new members are properly provisioned.
For more details and documentation, visit Slack API.
Note: When a custom invitation request management app is installed to an org, invitation requests will be sent to Org Owners and Admins. Workspace Owners and Admins will no longer receive invitation requests.