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SalehAlAdwan-4950 asked AndyDavid commented

451 4.4 0 primary target ip address responded with 421 4.4 2 connection dropped due to socket error

I have an issue between Exchange Server 2010 and Office 365; when I tried to send an email between office 365 and on premise Exchange Server 2010 or vice versa the emails stopped in Queue with this error "451 4.4 0 primary target ip address responded with 421 4.4 2 connection dropped due to socket error", even Hybrid Configuration Wizard failed to sync with O365, any help will be appreciated


office-exchange-server-mailflow
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Sounds like your firewall is blocking the necessary IPs.
Verify you allow the required IPs

https://docs.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?view=o365-worldwide#exchange-online

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Thank you for your quick response,
I think that my firewall is blocking the necessary IPs is NOT the problem reason; because when I use the Internet send connector the mail flow work properly, but when I use the send connector related to office 365 the previous issue appeared. NOTE: I can send emails to all other domains via Internet send connector from my on-perm Exchange 2010 Server.

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Have you verified that?
can you telnet on port 25 from the Exchange Server to office 365?
https://docs.microsoft.com/en-us/exchange/mail-flow/test-smtp-with-telnet?view=exchserver-2019




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SalehAlAdwan-4950 answered AndyDavid commented

Sorry for late in response,

Finally I solved my issues:

1) Regarding to mail flow issue between Office 365 and On-Premise & Vice Versa: Based on troubleshooting process we detected that there was an issue with TLS 1.2 negotiation between Office 365 and On-Premise & Vice Versa; so we enabled the TLS 1.2 on Exchange Server 2010 (on-premise), and we depend on the following Microsoft Article to solve this issue: SocketError when sending or receiving email messages - Exchange | Microsoft Docs and Understanding email scenarios if TLS versions cannot be agreed on with Exchange Online - Microsoft Tech Community, then test all the mail flow scenarios and all tests completed successfully.

2) Regarding to mailbox migration to office 365 issue “The connection to the server could not be completed”; we update the on-premise admin credentials on Migration part of office 365 then we re-run the Hybrid Configuration Wizard (HCW), and the migration patches started successfully.

Thank you all.

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You should upvote posts that helped you if you are going to make your own answer as accepted.

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AndyDavid answered SalehAlAdwan-4950 commented

If you believe that is the issue, then follow:
https://techcommunity.microsoft.com/t5/exchange-team-blog/exchange-server-tls-guidance-part-1-getting-ready-for-tls-1-2/ba-p/607649

Its in three parts, so read through all three sections and understand the implications before forcing TLS 1.2 on Exchange 2010.

You can verify if that is the issue by looking through the send connector SMTP protocol logs
You can enable by following:
https://docs.microsoft.com/en-us/exchange/mail-flow/connectors/configure-protocol-logging?view=exchserver-2019

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Thank you, I will check the exchange logs

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KyleXu-MSFT answered KyleXu-MSFT commented

@SalehAlAdwan-4950

You can also try to remove Office 365 related connectors, then rerun HCW to recreate them. Personally, I would suggest you disable firewall temporarily to check whether is this issue related with firewall.


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I did the following

In the regedit in the following registry Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

I Created a "TLS1.2" key, with "Client" and "Server" subkeys. In each subkey, I created a "DisabledByDefault" DWORD with a value of 0 and an "Enabled" DWORD with a value of 1.

and the send and receive emails issue between Exchange 2010 and Office 365 was solved, but for now the only problem still exist is I can not migrate any mailbox from on-prem to office365 using migration tab in EAC online, any assistance please

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This error details apear when I run test- migration server availability cmdlet:

internal error:Microsoft.Exchange.Migration.AutoDiscoverFailedConfigurationErrorException:
AutoDiscover failed with a configuration error: The migration service failed to detect the migration
endpoint using the Autodiscover service. Consider using the Exchange Remote Connectivity Analyzer
(https://testexchangeconnectivity.com) to diagnose the connectivity issues.
at Microsoft.Exchange.Migration.DataAccessLayer.MigrationEndpointBase.InitializeFromAutoDiscover(M
igrationEndpoint presentationObject, IMigrationAutodiscoverClient autodClient, SmtpAddress
emailAddress, Boolean acceptUntrustedCertificates)
at Microsoft.Exchange.Management.Migration.MigrationService.Endpoint.TestMigrationServerAvailabili
ty.InternalProcessExchangeRemoteMoveAutoDiscover()

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Any update about this thread now?

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Try to rerun HCW to update the configuration. Then create migration request from Exchange online side rather than "Office 365" tab which exist on Exchange on-premises EAC.

By the way, since the original problem has been solved, I would suggest you accepted AndyDavid's reply as an answer. Since discuss this new issue in another thread. It will convenient for community users to find the answers that match the title.

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