MessageTrace

Rising Flight 4,556 Reputation points
2024-09-29T21:23:12.4166667+00:00

Hi All,

I am using an Exchange 2016 hybrid environment. All my users are created on-premises and migrated to Exchange Online.One of my users, let's say user1@contoso.com, sent an email to a distribution list (DL) DL1@contoso.com. This DL has 1,000 members and is an Exchange Online Dynamic DL.However, user2 received the email even though user2 is not a member of the DL. I suspect there might be a forwarding rule, mailbox forwarder, or some other rule that caused the email to be sent to user2.Please guide me on how to trace this.

Microsoft Exchange Online
Exchange Server
Exchange Server
A family of Microsoft client/server messaging and collaboration software.
1,298 questions
Microsoft Exchange Online Management
Microsoft Exchange Online Management
Microsoft Exchange Online: A Microsoft email and calendaring hosted service.Management: The act or process of organizing, handling, directing or controlling something.
4,533 questions
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.
7,635 questions
Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
2,105 questions
0 comments No comments
{count} votes

Accepted answer
  1. Bruce Jing-MSFT 5,030 Reputation points Microsoft Vendor
    2024-09-30T05:59:11.8733333+00:00

    Hi,@Rising Flight

    Thanks for posting your question in the Microsoft Q&A forum.

    According to your description, when an email is sent to the Dynamic DL, members who are not members of the Dynamic DL receive the email.

    I have a couple more questions to confirm based on your question.

    1.Is this a problem for anyone sending emails to Dynamic DL?

    2.Is this email only forwarded to Users2?

    You can try the following:

    You can use Message Trace to see if messages are being forwarded by rules.

    I set up the following rule to simulate your current problem.

    User's image

    1. Sign in to the Exchange Administration Center (EAC) in Office 365.
    2. Navigate to Mail Flow and then Message Trace.
    3. Set the recipient to user2@contoso.com.

    If that email is forwarded by a rule, you can see a screenshot similar to the one below at Message events.

    User's image

    If my answer is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.

    0 comments No comments

0 additional answers

Sort by: Most helpful

Your answer

Answers can be marked as Accepted Answers by the question author, which helps users to know the answer solved the author's problem.