Entra ID B2B guest invitations blocked — "Invitations are blocked for this directory due to suspicious activity"

Question

Entra ID B2B guest invitations blocked — "Invitations are blocked for this directory due to suspicious activity"

Gitte Dreyer 30

We were developing and testing a script to automate the onboarding of external users via the Graph API. During development, we repeatedly invited and deleted the same user multiple times in quick succession to verify the script's behavior. We believe this pattern of rapid invite-delete cycles triggered the suspicious activity detection and caused the tenant-wide block on invitations.

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

Sridevi Machavarapu 33,820 Reputation points Microsoft External Staff Moderator

2026-03-18T09:25:35.1866667+00:00

Hello Gitte Dreyer,

As part of its security enhancements, Microsoft has anomaly detection systems in place to identify unusual activity, such as an unusually high number of invitations being sent from a tenant. If such anomalies are detected, the tenant may be temporarily blocked.

To unblock your tenant, we need few details to proceed further. Please check your Private messages tab and provide those details.
Drew Miller 0 Reputation points

2026-07-14T13:46:57.14+00:00

Same problem
Patrick Sullivan 0 Reputation points

2026-07-14T15:50:48.49+00:00

I have the same problem, question posed last week with no answers.

Answer accepted by question author

0 additional answers

Your answer

Sridevi Machavarapu 33,820 Reputation points Microsoft External Staff Moderator

2026-03-18T09:25:35.1866667+00:00

Hello Gitte Dreyer,

As part of its security enhancements, Microsoft has anomaly detection systems in place to identify unusual activity, such as an unusually high number of invitations being sent from a tenant. If such anomalies are detected, the tenant may be temporarily blocked.

To unblock your tenant, we need few details to proceed further. Please check your Private messages tab and provide those details.
Drew Miller 0 Reputation points

2026-07-14T13:46:57.14+00:00

Same problem
Patrick Sullivan 0 Reputation points

2026-07-14T15:50:48.49+00:00

I have the same problem, question posed last week with no answers.

Answer 1

The error indicates that Microsoft Entra has placed a security-based block on B2B invitations for the directory. This is treated as suspicious activity protection and cannot be cleared through configuration alone; it requires Microsoft support intervention.

Based on the available information, the only supported remediation path is:

Have a Global Administrator for the affected tenant open a support case with Microsoft.
In the support request, include:
- The exact error message and code from the Graph API response.
- A description of the recent activity pattern (repeated invite/delete cycles for test users).
- Confirmation that the activity was intentional and part of testing/automation.
Work with Microsoft support to review and remove the block on invitations for the directory.

While waiting for the block to be cleared, verify that normal B2B configuration is correct so that invitations work once unblocked:

Review External collaboration settings in Microsoft Entra to ensure:
- Guest invitations are allowed.
- The correct roles are permitted to invite guests.
- Any domain allow/block lists are configured as intended.
Review cross-tenant access settings and Microsoft cloud settings if collaborating with other Entra tenants or across Azure clouds, to ensure they are not independently blocking invitations.

If the tenant itself ever becomes inaccessible or blocked more broadly (for example, due to inactivity), a tenant administrator must also contact Microsoft support to request reactivation within the allowed window.

References: