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DKirschner's avatar
DKirschner
Copper Contributor
Feb 28, 2023

Connection refused when OnPrem is Offline

Hello,

we have a problem with the following configuration: we have a hybrid setup and all mailboxes are already on Exchange Online. The mails go via MX to a local mail gateway, which checks the mails for spam and then forwards them to Exchange Online. This works great so far.

We would like to switch off the HybridSetup soon. For this purpose we have switched off the OnPrem Exchange for a short time.
This has led to the fact that we have received no more mails from other Exchange Online tenants. The senders received the following error message:

 

 

 

2/28/2023 9:24:58 AM - Server at xyz.PROD.OUTLOOK.COM returned '550 5.4.316 Message expired, connection refused(Socket error code 10061)'
2/28/2023 9:20:16 AM - Server at mydomain.de (mySophosIP) returned '450 4.4.316 Connection refused [Message=Socket error code 10061] [LastAttemptedServerName=myDomain.de] [LastAttemptedIP=mySophosIP:25] [SmtpSecurity=-2;-2] [xyz.prod.protection.outlook.com 2023-02-28T09:20:17.672Z 08DB1932D1917656](Socket error code 10061)'

 

All other mail continued to go through without a problem.

After we restarted the local Exchange, all mails went through again without a problem.
What is happening that we could not get mails from Exchange Online Tenants anymore? Is this due to the hybrid setup and would it automatically resolve when we dissolve the setup? Or does it have something to do with the contruction of the external MX?

Thanks for any advice.

2016
exchange online
Exchange Server
hybrid

2 Replies

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  • Rana_Banerjee's avatar
    Rana_Banerjee
    Copper Contributor
    Mar 01, 2023

    Hello DKirschner,

     

    First of all I would strongly suggest that please do not turnoff your last exchange server until there is a proper way to do so. Currently there is none. If you turn off the last exchange server, you will need to use ADSI edit to manage certain aspects of your mailbox (eg enabling disabling archive).

     

    Now addressing your issue:

    If you have configured your Hybrid configuration in a regular way then it should not route any outbound emails from exchange online to Onprem except the hybrid mail flow traffic, instead it should directly route them either directly to the internet or via your 3rd party email gateway (depends on how you configured).

     

    The only reason it may route via onprem is if you have "Central Mail Flow" enabled within your hybrid configuration. Or have explicit transport rules which divert emails to on prem. There may be other reasons too but these are the most likely ones

     

    I request you to do the following:

    - while your on prem hybrid exchange is running, send some test emails which matches the scenario you had earlier. Then request the recipient to send across email headers (which is located in the email headers).

    - on the Hybrid exchange please run the following:

    PS:>$FormatEnumerationLimit = -1
    PS:>    Get-HybridConfiguration | select * | FL

    Please share the results with me via DM or email. 

     

    Please make sure to remove all sensitive information. 

     

    Kind Regards 

    Rana

    • DKirschner's avatar
      DKirschner
      Copper Contributor
      Mar 01, 2023
      Hello Rana,

      thank you for your answer.
      I'm not sure, but I probably didn't express myself precisely enough. I think you misunderstood the problem. The problem does not occur when I send mails, but when I receive mails (or not).
      I'll try to describe it again in more detail:
      Let's assume I am company A with domain_a.com. I have two customers, company B with domain_b.com and company C with domain_c.com.
      Company B runs its own mail server. Company C is also on Exchange Online.
      Both companies can send me mails normally in regular hybrid mode. However, as soon as the OnPrem is off, I no longer receive mails from Company C with the error message mentioned.
      Since the mails have to come to my mail gateway first according to MX, the problem should have nothing to do with my connectors (I have two of them), right? I have not activated any transport rules.

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