Connector validation

Question

Hi there,

I am trying to establish hybrid system based on using one domain (mydomain.com for example) and two mail servers- Exchange online and on-prem (non exchange) server hosted by 3th party. I plan to migrate only few users from on-prem to exchange online. On-prem server is our main server now. I added mydomain.com to my tenant and I set it as default one. Then I made a connector to enable sending e-mails from office 365 to on-prem users using the wizard from outlook admin panel. Validation at the end where successful and all test recipients located on on-prem server received validation e-mail from sender *@mydomain.com. Unfortunately when e-mail is sent from exchange online based user to on-prem server based user its receiving is unsuccessful. Returned error is 553 5.7.1 <@mydomain.com>: Sender address rejected: not logged in.*I am not sure if the 3th party server needs some additional configuration but why validation e-mail is received then?

I will appreciate any suggestions here.

Answer 1

Hello Georgi,

Thanks for your updates in PM with patience.

Based on the powershell result you provided in PM, the connector 3 you created from Office 365 to your partner organization is validated.  However, from the both message trace results ( successful and failed), the successful one is indicated with connector 5, and the powershell command you performed was associated with connector 3, may I double confirm if you created different connectors from Office 365 to your own server for mail flow?  You can go to Office 365 Exchange Admin Center > Mail flow > Connectors to double check it, if you have different connectors, please temporary disable/remove  the connector 3 and just keep the connector 5 to see if it make any difference.

Moreover, since the connector you created is validated, however it seems not triaggered when you sent emails to your own server, may I know when you created the connector, which option you choosed when to use the connector " Like For email messages sent to all accepted domain in your organization or only when email message are sent to these domains"?  Please double check the connector there, and if convenient, please choose the option " For email message sent to all accepted domains in your organization" at this time to see if it make any difference, thanks.

On another hand, I'd like to collect some more information for the accpted domains in your organization for further troubleshooting, please connect to the Exchange Online Powershell and then run the command Get-AcceptedDomain | FLafter that please share the full result to me in PM, thanks.

Best Regards,

Oliver

Answer 2

Hello Oliver,

I confirm that both users credentials are correct and they can sign in the mail app.

I confirm that validation is passed as successful and validation e-mail from sender ******@mydomain.com is well received at on-prem mail server without any errors.

Prerequisites for the server is performed. Port 25 is open and firewall is stetted up.

Since there is MX reccord forwarding all mails to other domain I added the SPF there. I can share the SPF validation on PM.

Results from outbondconnector is PMed to you

I confirm that emails sent to non-office 365 from external mail server are well sent and received by the recipients.

Answer 3

Hello Georgi,

Thanks for your detailed reply in PM with patience.

Based on the research on the NDR information you provided in PM, the NDR returned from your own server to online user. Based on the error message " not logged in", may I double confirm if the sender ( online user) and the recipient ( the mailbox in your own server) can sign in the its own email web app?  Please double check it, thanks. 

Moreover, since you mentioned the connector from Office 365 to your own server is validated OK, however the test email still reject by your own email server. And as far as I know the problem is more likely related to your own server side.  To further checking it, please help check if your own server is configured correctly to received the external email, and the the 25 port must be opened from the on-premises firewall.  Also make sure your firewall acceptps connections from all Office 365 IP addresses. For your reference https://docs.microsoft.com/en-us/office365/enterprise/urls-and-ip-address-ranges#exchange-online.   For more details about the Prerequisites that your own server need to be configured, please refer to https://docs.microsoft.com/en-us/exchange/mail-flow-best-practices/use-connectors-to-configure-mail-flow/set-up-connectors-to-route-mail > Prerequisites for your on-premises email environment.

And I also checked the domain you provided in the NDR, and found there is no Office 365 required DNS records were added to it, especially the SPF record, if there is no SPF record added, the email sender more likely regarded as not a valid sender. So please add it, thanks. For your reference Add DNS records to connect your domain (SPF).

On another hand, if the issue persists, I'd like to collect some more information for furthe troubleshooting:

1. The connector you configured, please refer to Get-OutboundConnector and check the results then share it with me via PM.
2. If you sent from a Non-Office 365 external email system to your own server, can it be received?

Best Regards,

Oliver

Answer 4

Hello Georgi,

Based on your description, my understanding is you are using connectors for mail flow between Exchange Online and your own  on-premises server, and currently you didn't deploy the Exchange Hybrid.  And according to your description, you have created a connector from Exchange Online to your own server, and it was validdated OK. As far as I know for using connectors to route mails between Exchange Online and on-premises Exchange server, you need create at least two connectors, one is from Exchange Online to on-premises server, and another one is from on-premises server to Exchange Online.  For more details, please refer to Set up connectors to route mail between Office 365 and your own email servers. Please double check if you have create them correctly, thanks.

Moreover, since the email cannot be sent from Exchange Online to your own server, may I know if you could sent from your own server to the online mailbox now? Please have a try at your convenience, thanks.

If the issue persists, I'd like to collect some more information for the further investigation:

1. the Full Non-Delivery Report message (NDR) / Returned error message.  
2. Since you mentioned your on-premises ( non Exchange) Seems it is not an Exchange server, may I know what server you have on the on-premises?

For protecting your privacy, I will send you a Private Message (PM) to collect the Full NDR, thanks.

Best Regards,

Oliver