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MrMind-2228 avatar image
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MrMind-2228 asked ·

Exchange EDGE tries to deliver via IPv6 even though it is disabled

I have on-premise Exchange deployment with EDGE server delivering email. The IPv6 has been disabled all along via Registry key. More and more local small companies are implementing IPv6 addressing and for some reason my EDGE server is trying o connect via IPv6 and can't, email goes to queue and sits there. If I tried to Retry email from the queue it get delivered via IPv4. Why is this happening?

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ZhengqiLou-MSFT avatar image
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ZhengqiLou-MSFT answered ·

Hi @MrMind-2228 ,

Have you checked the settings on the Connectors of Edge?
Also are you using the MX record or Smart host to route?

You can use the following command to check the IPAddress in using by your Edge send connector.

 Get-SendConnector -Identity "EdgeSendConnectorName" | FL Name,SourceIPAddress

Regards,
Lou


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MrMind-2228 avatar image
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MrMind-2228 answered ·

Yes, it is set to use MX record.

SourceIPAddress : 0.0.0.0

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Hi @MrMind-2228 ,

Sorry for the delay of this reply.
Please first make sure you have disabled the IPv6 correctly: Use registry key to configure IPv6

Are there any error messages(NDR) after the emails stuck in queue?
In EMS run Get-Queue to check the queue.
And also you can enable the protocol log on the Edge send connector: EdgeSync - Default-First-Site-Name to Internet.
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After sending the message, you could find the logs on the Edge server C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\Logs\Edge\ProtocolLog\SmtpSend

Best regards,
Zhengqi Lou

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Yes, I see many emails stuck in the queue, many with IPv6 as destination. I see in teh logs that EDGE server with properly disabled IPv6 still tries to connect to IPv6 address. Once I retry the message in the queue it actually connects to IPv4 of that receiver address.

BTW, I have IPv6 enabled on HUB servers. I'm thinking that sine HUB server has IPv6 enabled it gets IPv6 from DNS and tries to deliver email via EDGE. It can connect and email get stuck in the queue, once I retry on EDGE, EDGE server checks DNS, and since it does not have IPv6 enabled, it sees IPv4 of recipient server and successfully delivers emails.

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Hi @MrMind-2228 ,

Oh, you mean you're using Exchange 2010 right? Based on my knowledge, one of the function of the Hub transport server is to route e-mails sent from the internal organization to inside or outside. So you may consider to disable IPv6 on HUB server either to stop it.

Regards,
Lou

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