SMTP intermittency

Question

Hi - I am getting intermittent a lot of intermittency when using smtp.office365.com for SMATP.

Sometimes it works fine, other times it fails and there appears to be no consistency.

I have many different SMTP clients and am testing with the following script:

**Send-MailMessage -From ******@mydomain.com -To ****@somedomain.com -Subject "Test Email" -Body "Test SMTP Service from Powershell on Port 587" -SmtpServer smtp.office365.com -Credential $creds -UseSsl -Port 587

The credentials I am using are correct, there's no firewall involved, SMTP AUTH is turned on for the sending account. And this works perfectly end to end....until it doesn't. I have done some port testing using PortQuery and this shows that port 587 for smtp.office365.com seems to be listening half the time and filtered half the time.

It seems that the acceptance or dropping of the mail is dependent upon which IP the URL resolves to.

Is there any way to troubleshoot this further? It is frustrating to half half my notifications fail. I have also tested this with an IIS 6 SMTP relay - same thing, intermittency.

Thanks

GJB

Answer 1

Dear GJB_432,

Good day!

Thank you for posting to Microsoft Community. We are happy to assist you.

For the situation you encountered, we do understand the inconvenience you encountered and apologize for it.

From your mentioned description, we understand you are using SMTP AUTH client-submission and SMTP-rely, generally there are three options available to set SMTP, you can check it. For your reference How to set up a multifunction device or application to send email using Microsoft 365 or Office 365 | Microsoft Learn. In order to give a solution, we would like to confirm whether this inconsistency is occurred for inside or outside the organization emails?

On the other hand, please kindly check your internet and try to see the result via using different devices to send emails using Microsoft 365.

So, once you please try to setup another options from this above mentioned article and see the result.

Moreover, here is the detailed fixed issues related with SMTP, you can refer, it may provide some suitable information for you Fix issues with printers, scanners, and LOB applications that send email using Microsoft 365 or Office 365,.

If the issue still persist, as you mentioned "sometimes it works fine, other times it fails and there appears to be no consistency", since issue occurs sometimes, so to check this query further, required more technical resources and as we are belongs from Microsoft community site, we have limited resources, so for that we recommend to kindly contact our technical team via Get support - Microsoft 365 admin | Microsoft Learn, therefore they will check and assist you further.

We look forward to your update, Thank you for your precious time.

Stay safe and healthy. Have a nice day!

Sincerely,
Libeamlak | Microsoft Community Moderator