Suddenly Same email Delived to both primery domain email and email

Kanchana Jayathilake 0 Reputation points


we suddenly noticed one of our user getting same email deliverd to both primery SMTP and actual senarrio user only get one email but when we see the mail log we see it has deliverd to primery SMTP and second one has resolved.

my envirenment is one on-prem exchange which has migrated to M365 and two ads with azure connector.



Microsoft Exchange Online
Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Yuki Sun-MSFT 40,781 Reputation points

    Hi @Kanchana Jayathilake ,

    Is the MX record of your domain pointing to your on-premises Exchange organization while the user mailbox you mentioned above is hosted in Exchange Online?

    If both are true, it's actually the expected behavior. As in this scenario, inbound message will be delivered to on-premises Exchange server and then the on-premises Exchange server performs a lookup for each recipient using an on-premises global catalog server. When the global catalog lookup determines that the recipient's mailbox is located in the Exchange Online organization and has a hybrid routing address of, it will deliver the email to either account or the primary domain account.

    Reference: Transport routing in Exchange hybrid deployments.

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