Hello, @Jose TB,
Welcome to the Microsoft Q&A platform!
Based on your description, I understand that you encountered a situation where the original sender's data was not in the header after the email was forwarded through the server transport rules, affecting the proper functioning of the phishing filter.
To solve your problem, I have performed the following test.
- User A sends an email directly to user B. User B receives the email successfully, and the sender in the header is user A.
- Set up automatic forwarding for user C's mailbox, with the destination set to user B. User A sends an email to user C. User B receives the email successfully and the sender in the header is still user A.
I am using an Outlook mailbox for this test and the data shown in the header is always the original sender's data, regardless of whether automatic forwarding is enabled or not. It doesn't reproduce what you're describing. Regarding your reference to “Gmail data”, is that where I circled in the screenshot? This issue may be related to the Gmail mailbox you are using, do emails from Outlook have the same problem? I hope you will take the time to reply to me, it will help me to resolve your issue faster.
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Thank you for your support and understanding.
Best Wishes,
Alex Zhang