Exchange 2010 to 2016 migration problem

PaulH 41 Reputation points
2022-01-28T13:12:57.873+00:00

Ultimately we are trying to migrate from Exchange 2010 to Exchange online however we have to use 2016 as a stepping stone.

I have the 2016 server installed and working. I've created a test mailbox on the 2016 server to test mail flow. I can send mail to that mailbox all day but it cannot send out. Looking at the mail queues it shows the error:

4514.4.395 Target host responded with error. -> 451 5.7.3 Cannot achieve Exchange Server authentication

I've created individual receive connectors on each of the two Ex2010 servers just for this particular server with no auth necessary yet I still get this error.

Can anyone help?

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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  1. Andy David - MVP 140.8K Reputation points MVP
    2022-01-28T13:23:51.7+00:00

    Yea, no need to create custom receive connectors. The servers should be able to communicate out of the box. Was anything changed on the default 2010 connector


  2. Aaron Xue-MSFT 2,581 Reputation points Microsoft Vendor
    2022-01-31T06:31:24.357+00:00

    Hi @PaulH ,

    Agree with Andy. The issue sounds like the receive connector.

    And Exchange need to choose Exchange Server authentication to send internal mail flow.

    Here’s a similar case for you reference.
    https://community.spiceworks.com/topic/2239917-email-not-flowing-from-exchange-2016-mailbox-to-exchchange-2010-mailbox
    2239917-email-not-flowing-from-exchange-2016-mailbox-to-exchchange-2010-mailbox
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  3. PaulH 41 Reputation points
    2022-01-31T22:46:55.707+00:00

    I'm going to update this but I figured this out. There was another connector for non Exchange/Outlook connections that still had the IP address of the new Ex2016 server on it. Didn't seem to matter that I made the new connector first in the connector list. That old one seemed to have priority and disallowed the connection.

    Thanks for all the help.