💡 Our Technical Review in summary
1. Summary
Microsoft has resolved an issue where administrators were unable to create shared mailboxes within Exchange Online. The problem was triggered by a service update intended to optimize communication between Microsoft Entra and Exchange Online, which inadvertently caused a data type mismatch during the provisioning process.
2. Impact
Administrators attempting to create new shared mailboxes were blocked and typically received the error message: "Cannot convert a primitive value to the expected type 'Edm.Int64'." The issue persisted for approximately 10.5 hours on March 20, 2026.
3. Status
Service Restored. Microsoft has rolled back the specific service change responsible for the error. Health telemetry and internal testing have confirmed that shared mailbox creation is functioning normally. Microsoft is currently reviewing their testing and validation procedures to prevent similar regressions in future updates.
Microsoft Official Issue Details
User Impact
Admins may have been unable to create shared mailboxes in Exchange Online.
Status: serviceRestored
Service: Exchange Online
Classification: advisory
Origin: microsoft
Updates
- 2026-03-20 18:01
Title: Admins may be unable to create shared mailboxes in Exchange OnlineUser impact: Admins may have been unable to create shared mailboxes in Exchange Online.
More info: When admins attempted to create a shared mailbox, they may have received an error that stated, “Cannot convert a primitive value to the expected type ‘Edm.Int64’.”
Final status: We’ve identified that a recent service change meant to fix an issue with the communication between Microsoft Entra and Exchange Online caused impact. We’ve reversed the change and confirmed through service health telemetry and internal testing that the impact is remediated.
Scope of impact: Any admin that attempted to create a shared mailbox in Exchange Online may have been impacted.
Start time: Friday, March 20, 2026, at 6:10 AM UTC
End time: Friday, March 20, 2026, at 4:39 PM UTC
Root cause: A recent service change meant to fix an issue with the communication between Microsoft Entra and Exchange Online caused impact.
Next steps:
– While we investigate the reason our service change caused the impact, we’re reviewing our service change testing and validation procedures to identify and prevent similar issues in fixes moving forward.This is the final update for the event.
- 2026-03-20 16:27
Title: Admins may be unable to create shared mailboxes in Exchange OnlineUser impact: Admins may be unable to create shared mailboxes in Exchange Online.
More info: When admins attempt to create a shared mailbox, they may receive an error that states, “Cannot convert a primitive value to the expected type ‘Edm.Int64’.”
Current status: We’ve isolated a recent service change that we believe may be causing impact and we’re continuing to review this change to verify our theory.
Scope of impact: Any admin attempting to create a shared mailbox in Exchange Online may be impacted.
Next update by: Friday, March 20, 2026, at 6:30 PM UTC
- 2026-03-20 13:26
Title: Some users experience errors when attempting to create shared mailboxes in Exchange OnlineUser impact: Users experience errors when attempting to create shared mailboxes in Exchange Online.
Current status: We’re analyzing HTTP Archive format (HAR) logs to identify the underlying root cause and a mitigation plan.
Scope of impact: Your organization is affected by this event, and some users attempting to create shared mailboxes in Exchange Online may be impacted.
Next update by: Friday, March 20, 2025, at 5:30 PM UTC
- 2026-03-20 11:23
Title: Some users experience errors when attempting to create shared mailboxes in Exchange OnlineUser impact: Users experience errors when attempting to create shared mailboxes in Exchange Online.
As a workaround users are able to create a user mailbox and convert it to a shared mailbox.
Current status: We’re analyzing support provided information to determine our next troubleshooting steps.
Scope of impact: Your organization is affected by this event, and some users attempting to create shared mailboxes in Exchange Online may be impacted.
Next update by: Friday, March 20, 2025, at 1:30 PM UTC
