SMTP Relay to Office 365 Just stopped working with warning

Hi The Lucky,

Greetings. This is Alan Wu from Office 365 forum support. 

For your issue, I'd like to confirm whether you (your organization) has made any change before the issue occurs. I know it worked well from your description. And, for this issue, it might be caused that the firewall hasn't been enabled for 25 port. So, to isolate the issue, I suggest you can try sending from a different network environment to see if there is any difference. Meanwhile, here is a documentation for troubleshooting SMTP relay to Office 365 for your reference. https://support.office.com/en-us/article/fix-issues-with-printers-scanners-and-lob-applications-that-send-email-using-office-365-c75542a8-c792-42c0-a8c5-291df987512d?ui=en-US&rs=en-US&ad=US

If no difference, I'd like to collect the following information for further troubleshooting:

1. If there any NDR (Non-Delivery Report) generatedwhen you were trying to send. If so, please provide it in the Private Message (PM). 

2. Your detailed SMTP relay settings. Some related screenshots would be better. In consideration of the privacy, you can also provide the screenshots about the setting in PM. 

We are looking forward to hearing from you soon. 

Regards,

Alan

Dear Alan,

I believe we sorted out. We had to put UPN instead of form based authentication.

However we would like to setup unauthenticated mechanism. Because there are possibilities that after migration lot of device will be address where we would not have their sending email address ?

Like from and connecter in O365 and configure our SMTP public IP?

Kindly advice.

But my exact requirement is "Option 3: Configure a connector to send mail using Office 365 SMTP relay"

https://support.office.com/en-us/article/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-office-365-69f58e99-c550-4274-ad18-c805d654b4c4

Where I am using initially my SMTP server which I just configured.

By following this :-  https://support.office.com/en-us/article/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-office-365-69f58e99-c550-4274-ad18-c805d654b4c4

About connector configuration Kindly advice which connector I need to configure ( Inbound or outbound)? However, I have configured inbound already with these settings :

Connector type- On-premises

Sender Domain ( Verified domain)  And Public IP address for my SMTP server

And I am not getting any emails or in other words it's not working.

what should be a connector type partner or On-premises? Please keep in mind I am trying to achieve from newly SMTP relay configured server.

Kindly advice how we can achieve option 3.

Hi The Lucky,

Thanks for your clarification. 

Since you are using the Option 3 of https://support.office.com/en-us/article/how-to-set-up-a-multifunction-device-or-application-to-send-email-using-office-365-69f58e99-c550-4274-ad18-c805d654b4c4, the right procedure should be setting up one connector that is "from your organization's server to Office 365". This should be called "Inbound connector" as for Office 365. You can refer to the step-by step instructions described in the above documentation. 

Regards,

Alan

Dear Alan, what should be connector type partner or on-premesis?

And I configured my SMTP relay setup 

https://support.office.com/en-us/article/How-to-configure-IIS-for-relay-with-Office-365-eb57abd2-3859-4e79-b721-2ed1f0f579c9

From this I am able to send email If I choose authentication at outbound security.

However my motive is to go with PUBLIC IP based instead of authentication therefore I am going with option 3 https://support.office.com/en-us/article/How-to-set-up-a-multifunction-device-or-application-to-send-email-using-Office-365-69f58e99-c550-4274-ad18-c805d654b4c4

I have created inbound connecter and connector type is on-premises.

Configured accepted domain ( verified) and public ip change the port in relay config 587 to 25 

, I have no idea what I am missing here ?

Can you help..to merge these article to my troubleshooting ?

I tried to put all this together.

in SMTP relay

Anonymous authentication and MX record as smart host along with port 25.

Message delivery to the host <removed by moderator for protecting your privacy> failed while delivering to the remote domain 'u******.com.au' for the following reason: The remote server did not respond to a connection attempt. 

Hi The Lucky,

Thanks for working on this isssue with us. I have covered the host address in your last reply for protecting your privacy. 

For the host "**.**.**.***" the error message said, I'd like to know if it is your IP address. If yes, please add it to your SPF record to see if it helps. The SPF record should be v=spf1 ip4:<Static IP Address> include:spf.protection.outlook.com ~all. 

If the issue persists, please provide the complete NDR in the PM so that I can help analyze it. 

Regards,

Alan

Hi The Lucky,

If you got an update, please let me know. With pleasure, I am always here for you. 

Regards,
Alan