Invitations are blocked for this directory due to suspicious activity. Please contact Microsoft support for help

Hello Microsoft Support,

Tenant ID: 

We are experiencing a critical issue with our Azure AD tenant. All guest invitations are now failing with the following error from the Graph API:

{ "error": { "code": "Forbidden", "message": "Invitations are blocked for this directory due to suspicious activity. Please contact Microsoft support for help."}" }

Context of Issue: We are the Global Administrators for this tenant. As part of a planned bulk onboarding process, we used the Microsoft AZURE portal bulk invitation feature and the Graph API to invite approximately 13000 users in multiple CSV batches. These users are legitimate customers/partners for our organization who need access to our systems.

After several bulk invitation operations over a short period, all further invitations began failing—even single manual invites in the portal. The error message indicates our directory’s invitation capability is now completely blocked due to suspected abuse.

Impact:

We can no longer invite any new guests.
Our onboarding of legitimate users is fully blocked.
This is affecting critical business operations and timelines.
Request:

Please review and remove the "suspicious activity" block on our directory's invitation capability.
Please confirm any guidelines or best practices to avoid hitting this block in the future.
We can provide our invitation CSV files, details of our process, and business justification for this bulk onboarding if needed.