Office 365 Shared Mailbox - Repeatedly sending NDRs to mailer daemon, now reached "message limit" and cannot reach customers

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  Hello,

  We have a shared mailbox that is set to Auto-Reply to customers when they email our customer service mailbox. Occasionally it will get stuck in a loop of some sorts, where it constantly sends NDRs to a Mailer Daemon, which in turn gets rejected and sent back to us since the email address is invalid. I am unsure if this is a Backscatter issue, though I have enabled the backscatter protection to be safe. We have also tried turning on transport rules to block messages sent to addresses containing Mailer-Daemon as well as added the Mailer-Daemon's domain to spam filter blacklist for now until we figure it out.

  Normally it's just annoying, however today one of our users got an error trying to send an email that we've reached out daily limit for message recipients. I don't think it's actually for message recipients since I believe most of these emails are being sent to one address. This is now impacting our ability to reach our customers in a timely matter so I am looking for a resolution to this as soon as possible. Wondering if anyone has advice or can help me at all?

  • Moved by Steve Fan Tuesday, June 27, 2017 5:37 AM Move to dedicated Outlook forum

  Monday, June 26, 2017 5:38 PM