Exchange Online automatic forwarding no longer preserves forwarded recipient in Microsoft Graph or MIME headers

Hi Abhi Dashadiya,

Thank you for reaching out and for the detailed information regarding the forwarded recipient address no longer appearing in messages retrieved through Microsoft Graph after Exchange Online mailbox level forwarding.

This change is connected to a recent update in the way Exchange Online handles transport headers during cross tenant mail forwarding. As you noted, the X-MS-Exchange-Transport-CrossTenantHeadersStripped header confirms that certain metadata is now being removed for privacy and security reasons when a message crosses tenant boundaries. Consequently, the original forwarded recipient is no longer preserved in the toRecipients field, internetMessageHeaders, or raw MIME content once the message reaches your application through Microsoft Graph.

To address this matter effectively, please follow the steps below, as they will suit your situation. If you don't have a permission, please contact your IT's administrator to follow this steps below:   

1/ Verify forwarding behavior through message trace (admin only)

• Run a message trace in the Exchange Admin Center or through the Microsoft Graph reportRoot API for the affected mailbox  
• Confirm whether the forwarding metadata is still logged at the transport level, even if it no longer appears in the delivered message
• This helps establish whether the recipient information is simply hidden from the message body or removed entirely
• Reference: Run a message trace and view the results in the Exchange admin center in Exchange Online | Microsoft Learn

2/ Preserve the forwarded address with a mail flow rule

• Go to the Exchange Admin Center.    
• Navigate to Mail Flow > Rules
• Create a mail flow rule (transport rule) that inserts a custom header containing the forwarded recipient address before the message leaves the tenant
  • This embeds the forwarding information directly into the message, so it is independent of the default header stripping behavior
  • Reference: Mail flow rule actions in Exchange Online

3/ Use redirect instead of standard forwarding

• Since mailbox level automatic forwarding is subject to the new header stripping policy, consider switching the mailbox to an Inbox Rule using the "Redirect" action instead
• Redirect delivers the message without altering the envelope in the same way forwarding does, and may retain additional original message properties
• References: Configure email forwarding for a mailbox in Exchange Online and All you need to know about automatic email forwarding in Exchange Online

If the issue persists after these checks, ask your IT administrator to submit a support request directly to Microsoft Support team and attach the Microsoft Graph JSON response, raw MIME sample, and the Gmail comparison you already prepared. In this cases, further investigation may be required at the service level, which is not accessible through standard administrative tools. 

The Microsoft Support team has the capability to review backend service behavior, analyze logs not available to administrators, and identify any underlying issues affecting message delivery.     

A support ticket can be created via the following link: Get support - Microsoft 365 admin | Microsoft Learn 

In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support    

Or you can contact them via phone number to Microsoft Support: Customer service phone numbers - Microsoft Support - Select your country/region own phone number for support.   

As forum users, we appreciate your understanding that our access to internal development details is limited. Our primary role is to guide users toward the appropriate resources and support channels. While we may not have visibility into deeper backend analysis, we’ll continue doing our best to support you within the scope of our responsibilities.           

I hope this information is helpful. Please follow these steps and let me know if it works for you. If you have any updates regarding the issue, please feel free to share them with me.            

Thank you for your patience and your understanding. I look forward to continuing the conversation.  

If the answer is helpful, please click "Yes". If you have extra questions about this answer, please click "Comment".  

Note: Please follow the steps in the forum documentation to enable e-mail notifications if you want to receive the related email notification for this thread.