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Some users may not see free/busy info shared between organizations using cross-tenant access policy in Exchange Online

Exchange Online EX1542065

Users may not see free/busy info shared between organizations using cross-tenant access policy in Exchange Online.

Status
Service degradation
Feature
OWA - poor customer experience
Region
Not specified (all regions)
Started
Nov 4, 2026, 17:00 CET
Duration
7 days 8 h
Last update
Nov 12, 2026, 00:48 CET
Next update
Nov 13, 2026, 01:00 CET

Current status

After further analysis, we've isolated that additional organizations utilizing cross-tenant access policies are affected by this free/busy issue, and we've expanded communications to all potentially affected users. We've updated the "Title", "User impact", and "Scope of impact" fields of our communications to reflect this. We've initiated deployment of a fix to address a regression introduced by a recent service change that caused cross-tenant mailbox requests to be rejected when a tenant ID was used instead of the mailbox's SMTP address. We're evaluating ways to expedite our deployment and we aim to provide a timeline to remediation as soon as possible

More info

To remediate impact while our investigation is ongoing, admins can configure free/busy sharing between impacted organizations using Organization Relationship. The Organization Relationship will take precedence over the cross-tenant access policy and sharing will begin working again after caches clear, usually within 2 hours. If EWS has been disabled in your tenant, it will need to be re-enabled to support Organization Relationship. The Organization Relationship should be removed when this incident is resolved.

More information on this process can be viewed here: https://learn.microsoft.com/en-us/exchange/sharing/organization-relationships/create-an-organization-relationship

Scope of impact

This issue impacts some users whose organization utilizes cross-tenant access policy, who may be unable to view free/busy info shared between organizations in Exchange Online. This section may be updated as the investigation progresses.

Root cause

A recent change introduced a regression that causes cross-tenant mailbox requests to be rejected when a tenant ID was used instead of the mailbox's SMTP address.

Timeline

Every update Microsoft posted for this issue, newest first.

  1. Nov 12, 2026, 00:22 CET

    After further analysis, we've isolated that additional organizations utilizing cross-tenant access policies are affected by this free/busy issue, and we've expanded communications to all potentially affected users. We've updated the "Title", "User impact", and "Scope of impact" fields of our communications to reflect this. We've initiated deployment of a fix to address a regression introduced by a recent service change that caused cross-tenant mailbox requests to be rejected when a tenant ID was used instead of the mailbox's SMTP address. We're evaluating ways to expedite our deployment and we aim to provide a timeline to remediation as soon as possible

  2. Nov 11, 2026, 20:44 CET

    We've completed validation of our code fix to revert the service change responsible for this issue and have initiated deployment to the affected environment. As deployment progresses, some users may begin experiencing impact alleviation. We'll provide an estimated resolution timeline once available.

  3. Nov 10, 2026, 20:35 CET

    We're validating our code fix that'll revert the offending service change, address the offending regression, and remediate the impact. We'll provide an updated timeline for the deployment of our code fix after our internal validations have verified that its deployment won't produce any unexpected problems for the service.

  4. Nov 10, 2026, 10:28 CET

    We've identified that a recent change introduced a regression that caused cross-tenant mailbox requests to be rejected when a tenant ID was used instead of the mailbox's SMTP address, resulting in impact. We're reverting the change to restore the correct configuration and expect to confirm the deployment timeline by our next scheduled update.

  5. Nov 10, 2026, 05:53 CET

    After further investigation, it was determined that additional information from affected systems and users regarding recent mailbox migrations would be required to facilitate remediation efforts. We're reaching out to your representatives to gather additional diagnostic logs to help with understanding the underlying root cause.

  6. Nov 10, 2026, 04:15 CET

    Our investigation into data migration configurations is progressing, however due to the complexity of the issue this is taking longer than initially anticipated. We're reviewing telemetry relevant to affected systems and will provide an updated timeline on remediation as one becomes available.

  7. Nov 10, 2026, 02:25 CET

    Our review of the database mismatch mentioned in previous communications is ongoing. In parallel, we've expanded the investigation and are examining configuration settings and system telemetry to identify and isolate potential errors which may have occurred during recent data migrations to determine whether these could be contributing to impact.

  8. Nov 9, 2026, 23:57 CET

    We're analyzing a database mismatch from free/busy information requests shared by your representatives to isolate if this is the underlying source of impact and to evaluate our next steps towards remediation.

  9. Nov 8, 2026, 02:13 CET

    Our review of the recently provided data from your organization has been inconclusive. Subsequently, we’ve begun to reach out to your representatives to gather several reproductions of impact as we anticipate that these items will expedite our investigative efforts and help determine our next troubleshooting actions.

  10. Nov 7, 2026, 06:23 CET

    We’ve collected the read-only outputs containing information about your organization's relationship and connector settings and are working on correlating its GetSchedule requests to the failures observed in the HAR so that we can identify the underlying root cause and develop a remediation plan.

  11. Nov 7, 2026, 01:47 CET

    We're continuing our investigation of HAR logs and have determined that additional information about your organization's relationship and connector settings is needed to better understand the issue and identify remediation steps. We're coordinating with your representatives to collect these details.

  12. Nov 6, 2026, 23:47 CET

    We’ve received the requested fresh HAR logs and are analyzing them to identify and isolate any errors potentially contributing to impact for further investigation.

  13. Nov 6, 2026, 22:50 CET

    We’re reaching out to your representatives to request fresh HTTP Archive format (HAR) logs to assist our investigation into the source of the issue.

  14. Nov 6, 2026, 22:33 CET

    We're investigating a potential issue with Exchange Online and checking for impact to your organization. We'll provide an update within 30 minutes.

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