External messaging limits for onmicrosoft.com-only organizations in Microsoft Teams

🚨 The Signal: Microsoft Teams will enforce outbound external messaging limits for organizations using only the default onmicrosoft.com domain. This aims to prevent spam and phishing, temporarily restricting external chats if limits are exceeded.

The Impact

Organizations relying solely on the onmicrosoft.com domain face a low security risk, as this change improves protection against external abuse.

• External users: May experience temporary inability to receive messages from affected organizations.
• Affected organizations: May see temporary blocks on outbound external messages if limits are hit.
• Security teams: Benefit from reduced spam and phishing vectors originating from their tenant.
• Admins: Need to be aware of potential user queries regarding external messaging blocks.

The Action

1. Review your organization's domain configuration in Microsoft 365 admin center.
2. If using only onmicrosoft.com, consider adding and configuring a custom domain for Teams.
3. Communicate to users that external messaging limits are in place to combat spam and phishing.

Domain: Teams · Impact: low · Workload: Teams