Emails to blocked

MrJim Johnson 1 Reputation point

My customers are not getting confirmation emails. They are being blocked.

This is in the bounced email notification.
" ----- Transcript of session follows ----- .. while talking to

>> MAIL From:<>

<<< 550 5.7.1 Unfortunately, messages from [] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to []

Getting same message [with one word changed] on emails sent to

I cannot contact anyone at Microsoft that knows what is going on. Was told by an MS Exchange support tech that there is no way for MS to block them.

I am close to my email provider support team, I have their cell phone numbers. And they can't find out what's going on. Nor can they contact MS.

Any ideas would be helpful.

Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Jame Xu-MSFT 4,171 Reputation points

    Hi @MrJim Johnson ,
    Based on your error message “550 5.7.1”, you can refer to this document:
    You can get in touch with Outlook Sender Support via going to this direct link:
    In addition, please pay attention to protect your private information, thank you.

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