Getting 530 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM

DawidKroll 20 Reputation points
2024-06-05T06:29:09.7166667+00:00

Hi,

we are getting Mailflow Issues "530 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM"

when Email comes from External or Internal to an OnPrem Mailbox Exchange 2016. We have a Hybrid Setup. Normally this Error would show up if this Mail would come from an Application or Device, but its from a normal User.

But the Problem is, it happens sporadically. It started on 6/3/24.

Thanks,

Microsoft Exchange Hybrid Management
Microsoft Exchange Hybrid Management
Microsoft Exchange: Microsoft messaging and collaboration software.Hybrid Management: Organizing, handling, directing or controlling hybrid deployments.
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Accepted answer
  1. Noah Ma-MSFT 2,085 Reputation points Microsoft Vendor
    2024-06-11T07:47:44.0166667+00:00

    Hi Dawid,

    Great to know that the issue has already been resolved and thanks for sharing the solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I'll repost your solution in case you'd like to Accept the answer : )     

    --------------   

    Issue Symptom: 

    Got an error message “530 5.7.57 SMTP; Client was not authenticated to send anonymous mail……"

     

    Resolution: 

    Caused by allowed only specific IPs from MS and it turns out after allowed everything that mail began to flow again.

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  1. Noah Ma-MSFT 2,085 Reputation points Microsoft Vendor
    2024-06-06T09:23:04.6733333+00:00

    Hi @DawidKroll,

    Thank you for posting to Microsoft Community.

    Based on your description, I want to confirm with you if you mean there is a “Client was not authenticated to send anonymous mail” error when you send emails.

    You may be using the SMTP client submission endpoint (smtp.office365.com), which can't be used for direct send for direct send. Please check the MX record for your O365, which ends with "mail.protection.outlook.com and change the SMTP port is 25/TLS. You could refer to How to set up a multifunction device or application to send emails using Microsoft 365 or Office 365 | Microsoft Learn for more information.

    Also, please ensure Multi-Factor Authentication is disabled and kindly check Azure Security Defaults setting is also in disable.

    For more information, please refer to Error: Authentication unsuccessful.

    Hope it helps, if there are anything I misunderstood or I could help, please let me know.

  2. Rania Zaid Ali Salim Zaid 0 Reputation points
    2024-06-11T11:04:14.0366667+00:00

    thanks for the answer

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