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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?
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
Nothing was changed by me prior to install of the Ex2016 server. The 2010 servers were also at the latest service level prior to 2016 install.
Can you disable those custom receive connectors on the 2010 side?
Then check the Default mailbox connector on the 2010 server. :
https://blog.rmilne.ca/2018/04/03/exchange-2010-default-connector-configuration/#:~:text=Default%20Receive%20Connectors%20Overview&text=The%20%E2%80%9CDefault%20%E2%80%9D,used%20for%20client%20SMTP%20submission.
Scroll down to the receive connector configs and make sure they match what is that doc from Rhoderick
Ok I have disabled the custom connectors and re-added the full internal subnet to the default so that it again includes the Ex2016 server. I have compared the default connectors and for the most part they are identical to the ones in the site you reference except for a couple of things. Notable the IP addressing they have includes anything and everything. Ours includes only pertinent subnets. The other things is under the Permissions groups tab "Anonymous" is checked. Should I remove that?
On that note I am still getting the error. What else can I look at?
Edit: Where are the logs that would show errors? I can see connections in the SMTP log but it doesn't show any error whatsoever.
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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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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.
Yep! Glad you fixed it. :)
Hi @P a u l ，
Glad to hear that your issue has been solved.
I'd appreciate it if you choose the most helpful post above and mark it as the best answer, this will make answer searching in the forum easier and be beneficial to other community members as well.
Thanks!