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External recipients receive multiple duplicate meeting invitation emails?

    Question

  • Hello folks,

    We're having an issue with our users sending meeting invites to users with external email accounts. The invitation includes recipients with both internal and external mailboxes - the internal users receive one copy of the message, but the external recipients receive up to ten duplicates of the same invitation.

    In the output from our message tracking log, it looks like our Exchange server is sending duplicates:

    I'm not exactly sure what this means or how to address it. Any help would be appreciated.

    Thank you!

    Wednesday, March 29, 2017 3:02 PM

All replies

  • Hello,

    To narrow down your issue, I want to confirm:
    1. Is it this issue occurs on some special mailbox or client? How about OWA?
    2. Are there multiple duplicate message in sender's Sent Item folder?
    3. Check the message header and ensure the message ID is same or not.

    From your screenshot, the message seems submit again.
    Thus, if this issue only occurs on some special client, run Outlook with safe mode and check the results.

    Meanwhile, run below command to check the message tracking log:
    Get-MessageTrackingLog -MessageSubject "duplicate Message" | fl  MessageID,TimeStamp,Event*,Recipients,MessageSubject,Sender,ReturnPath

    Best Regards,

    Allen Wang


    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Thursday, March 30, 2017 8:02 AM
    Moderator
  • Thanks for your helpful reply.

    The issue has occurred for two of our users who set up a recurring meeting. There are no duplicates in the sender's Sent Items folder.

    We believe this could possibly be caused by the users mobile device - when searching the tracking log, the "ClientType" for the message that contains duplicate recipients is AirSync.

    We have instructed the user to turn off syncing on his phone before the next meeting email and to recreate the meeting from scratch once syncing is turned off. We will then see if duplicates are still generated.

    Thank you.

    Monday, April 3, 2017 7:27 PM
  • You're welcome, and thanks for your sharing.

    If it works and solves, please be free to mark the useful information as mark. Thanks again.

    Best Regards,

    Allen Wang


    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Friday, April 7, 2017 3:30 AM
    Moderator