the header X-MS-Exchange-CrossTenant-id is missing

Dear Memo it，

Thanks for choosing Microsoft Community.

Based on your description, I know your requirement. Since your issue is about header of the Cross Tenant. I am willing to help you but it is really out of support scope. In order to better help you, please kindly try to create a service ticket in the Office 365 admin center(Microsoft 365 admin center) by navigating to support > service requests, as they have more access than on this forum, which will help you further. Believe they can help you solve your problem.

Note: If you don‘t use admin account, please kindly to ask admin within your organization for help.

Thanks for your precious time. Have a nice day.

Sincerely,

Katherine

We started having this same issue today. We contacted Microsoft Support and have a case going. They did indicate they saw other customers with a particular third-party email relay service provider having the same issue. The root issue is the x-ms-exchange-crosstenant-id message header entry is missing. It was there yesterday, not sure where it went early this morning!

We started to see the behavior as well.

@Kathrine Yu - such infrastructure changes shall be communicated via release notes/update info, could you point me to the direction?

We could create a ticket as well, but wouldn't that just jam the support queue?

From my understanding:

This Header "X-MS-Exchange-CrossTenant-ID" was never published somewhere for other than internal usages and is has already disappeared on most of my tenants and customer tenants. And we used it a lot for rules and 3rd Party solution. But is it gone and someone told me, that it will disappear on all tenants.

There is another header, which is documented on some pages:

X-OriginatorOrg

I contains the SMTP-Domain of the sender (so longer a GUID of the tenant and if you have multiple domains, you have to define them all in rules or where you use them.

• Establishing Exchange Hybrid Mailflow
  https://www.youtube.com/watch?v=1i_SO6nKe0o&t=605s
  "Organization

   Headers are preserved" ad Minute 10:05

• Advanced Office 365 Routing: Locking Down Exchange On-Premises when MX points to Office 365
  https://techcommunity.microsoft.com/t5/exchange-team-blog/advanced-office-365-routing-locking-down-exchange-on-premises/ba-p/609238
  See the usage of the rules

I blogged some days ago at https://www.msxfaq.de/cloud/exchangeonline/transport/x-originatororg.htm  (German, maybe Bing/Google/deepl may help you to read it in our language

So start changing your logic to use that header instead

Frank