SMTP Relay

Question

SMTP Relay

Mohamed jihad bayali 1,136

Hello,

I have an issue, here is my situation : Our users have exchange online mailboxes, and our servers are using an smtp relay to send emails. The issue is that, i cannot send emails to external domains using the local SMTP relay, but i can send emails internally using the local SMTP Relay.

Any idea from where the issue can come from? on the m365 side, except the public ip adress that should be allowed on the M365 connectors, is there any thing that need to be checked?

Thanks

Andy David - MVP 153.7K Reputation points MVP

2024-01-16T17:07:10.6466667+00:00

What happens when you try to send the messages? Whats the error message or NDR? Did this work before?
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Mohamed jihad bayali 1,136 Reputation points

2024-01-16T17:20:36.9833333+00:00

Exchange online
Mohamed jihad bayali 1,136 Reputation points

2024-01-16T17:24:26.7+00:00

Hello Andy,

I writed a comment, but i don't why it dissapeared.

I wanted to tell you that i did try to send mails from the smtp using send-mail (powershell command), when sending mails to an adress on the organization's domain it works, but when sending a mail to an external domain, there is no error after launching the command, but the email isn't send + there is no trace of the mail in M365 (Explorer).
Know that the external domain that i'm sending the email to is well declared as accepted domain I still didn't check the connector configuration on m365, i will check them tomorrow with my colleagues, i dont know if you ever encountered a similar issue or if you have some strong leads

Thanks

2 answers

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Andy David - MVP 153.7K Reputation points MVP

2024-01-16T17:07:10.6466667+00:00

What happens when you try to send the messages? Whats the error message or NDR? Did this work before?
Deleted

This comment has been deleted due to a violation of our Code of Conduct. The comment was manually reported or identified through automated detection before action was taken. Please refer to our Code of Conduct for more information.
Mohamed jihad bayali 1,136 Reputation points

2024-01-16T17:20:36.9833333+00:00

Exchange online
Mohamed jihad bayali 1,136 Reputation points

2024-01-16T17:24:26.7+00:00

Hello Andy,

I writed a comment, but i don't why it dissapeared.

I wanted to tell you that i did try to send mails from the smtp using send-mail (powershell command), when sending mails to an adress on the organization's domain it works, but when sending a mail to an external domain, there is no error after launching the command, but the email isn't send + there is no trace of the mail in M365 (Explorer).
Know that the external domain that i'm sending the email to is well declared as accepted domain I still didn't check the connector configuration on m365, i will check them tomorrow with my colleagues, i dont know if you ever encountered a similar issue or if you have some strong leads

Thanks

Answer 1

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Answer 2

Wandi Ding -MSFT 2,965 Microsoft External Staff

Hello @Mohamed jihad bayali ,

As Andy asked, have you encountered this problem before? Also, have you made any recent changes? Could you please check the event viewer to see if there is any relevant information.

As you mentioned, please ensure that the connector configuration is correct and that the IP address of your SMTP relay is added to the allowed list. Besides, it's a good idea to verify that the SMTP gateway can correctly resolve the MX records of the external domain. You could try using the nslookup command to verify this. Additionally, it is recommended that you check your firewall to ensure that it's not blocking outbound SMTP traffic.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment". Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Mohamed jihad bayali 1,136 Reputation points

2024-01-17T07:20:41.2066667+00:00

Hello Wandi,

It is a new domain, we just added it as accepted domain on the SMTP GW, and the M365 created the connector. DNS resolution is working correctly on the SMTP Server

Any leads?

Regards
Wandi Ding -MSFT 2,965 Reputation points Microsoft External Staff

2024-01-19T08:14:07.63+00:00

Hi, thank you for your update. Based on your feedback, it is speculated that there may be a problem with the connector configuration. It is recommended that you verify that the connector configuration is correct, including correct authentication settings and any required TLS settings. Could you check the message trace logs to see if there are any errors or issues with messages sent to external domains.
Wandi Ding -MSFT 2,965 Reputation points Microsoft External Staff

2024-01-24T08:50:14.28+00:00

Hello, I'm here to confirm the progress of your thread, has your problem been solved? Could you kindly let me know if you need any further assistance? If the method provided helps you fix the issue, you could mark the answer to help people who have the same issue :)

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SMTP Relay

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