Mail from internal application still not being relayed to recipients of distribution group

Nur Hossain 21 Reputation points
2020-08-26T08:48:41.553+00:00

But if I changed the delivery management setting from "Only senders inside my organization" to "Senders inside and outside of my organization" and I was then able to telnet to exchange from the application server in question and send the email to the distribution group in question and I see it went out to all of the recipients in the DG.

Although it is working in this way, it's not ideal, as now anyone from the outside can also send email to that DG.

So what is the better solution to this problem? Adding the Exchange server permission to the SMTP Relay receive connector.

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.
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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.
7,348 questions
Accepted answer
  1. Lydia Zhou - MSFT 2,371 Reputation points Microsoft Employee
    2020-08-27T02:44:04.257+00:00

    Except solutions provided by michev, there is another workaround for you.

    Do you mean you want to set that DG can only receive messages from internal users and the application server?
    If so, we can create a mail flow rule to block external messages sent to this DG, except the sender address used by your application. However, please pay attention that, if an external message sent to this DG and other internal users are added as recipients, other internal users won't receive this message as well.

    You can create the rule like this:
    Apply this rule if "the sender is outside the organization" and "The message To or Cc box contains DG", reject the message and include an explanation. Except the sender is the application address.

    20774-546.png

    If the response is helpful, please click "Accept Answer" and upvote it.

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  1. Vasil Michev 95,181 Reputation points MVP
    2020-08-26T09:18:05.08+00:00

    To be considered "internal", the application either must use an Exchange account, or you can add the externally secured flag, as detailed for example here: https://learn.microsoft.com/en-us/exchange/mail-flow/connectors/allow-anonymous-relay?view=exchserver-2019

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  2. Dominique Pollard 46 Reputation points
    2020-08-27T04:17:52.067+00:00

    I'm wondering are you by chance hybrid or Cloud Only implementation? I have seen that the hybrid configuration wizard is ran and each environment sees the other as external in hybrid.