Send /Outbound connector on Exchange and Exchange Online

GoodResource 381 Reputation points
2022-01-19T07:20:13.727+00:00

Hi,
I have two queries as below:

  1. IN Exchange Online, Outbound connector can we use private IP address of an on prem smart host? Or does it always have to be Public IP address?
  2. IN Exchange Server on premise 2016, send connector, can we use private IP address of an on prem server/smart host? Or it also has to be public IP address?
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.
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Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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Accepted answer
  1. Andy David - MVP 147.9K Reputation points MVP
    2022-01-19T12:57:42.587+00:00

    First Question: Public, Exchange Online will have no way of finding it and connecting otherwise:
    https://learn.microsoft.com/en-us/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/set-up-connectors-to-route-mail

    166310-image.png

    Second question: Depends. If the private IP is on your network or accessible via VPN or internal way to get to that other network,, then yes.
    If the recipient is external and you have no private, internal path to it, then it must be an external IP listed n the smarthost.

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