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Exchange 2016 ndr taking too long to return

Elias Chamoun 21 Reputation points
2020-12-03T13:53:28.843+00:00

Dear Sirs,

I have an exchange 2016 setup only for internal use and there's no send connector configured.

on the outlook client side, I have setup 2 mail accounts one with exchange and to other with an external POP and SMTP that we use for sending emails outside the domain.

the problem I'm facing is that when the users send an email to the outside world using the exchange account by mistake.

the NDR reply from the exchange server takes about 2 days to get back and the users assume that their email was sent. to find out after 2 days that they sent from the wrong account.

I tried to modify the parameters in the edgeTransport.exe.config file and the parameters in ECA with no luck.

is there's a way to make exchange NDR reply immediately? or is there's a way to deny users from sending email from exchange on outlook?

thank you so much for your support

Exchange | Exchange Server | Management
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Accepted answer
  1. Andy David - MVP 157.8K Reputation points MVP Volunteer Moderator
    2020-12-03T14:10:05.167+00:00

    Its taking 2 days because its probably queuing and trying to send the message.
    Why not just use Exchange for messaging? Why the POP usage?

    Is the SMTP server separate from Exchange?

    If so, and you want to prevent sending to the outside via Exchange, I would create a transport rule that rejects the message sent to outside immediately:

    Example:

    44852-image.png

    1 person found this answer helpful.

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  1. Lydia Zhou - MSFT 2,386 Reputation points Microsoft Employee
    2020-12-04T02:57:03.793+00:00

    @Elias Chamoun

    Agree with AndyDavid, you also can use message tracking log to see the mail flow for that message: 

    Get-TransportService|Get-MessageTrackingLog -MessageSubject <subject> -Sender <mailbox address> -Recipients <mailbox address> |select timestamp,EventID,Source,ConnectorID|sort-object Timestamp

    You can try to create the mail flow rule as AndyDavid mentioned to block messages sent to the external. It works well in my environment:
    44968-629.png

    44946-628.png

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    1 person found this answer helpful.

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