In this post, let’s have a look at the error message “5.7.57 – Client was not authenticated to send anonymous mail during MAIL FROM” that you get when working with Microsoft 365 Exchange Online.
These are the errors that you usually receive when there is a problem in delivering the email message that was sent by you. These errors are generated and sent by Office 365. This is usually alled as DSN which stands for delivery status notification or in simple words bounce messages.
NDR or Non-delivery report is one of the common type of message that you receive which indicates to the user that the email was not delivered.
5.7.57 – Client was not authenticated to send anonymous mail during MAIL FROM
You configured an application or device to send (relay) email messages in Microsoft 365 or Office 365 using the smtp.office365.com endpoint, and there’s a problem with the configuration of the application or device.
For more information, see Fix email delivery issues for error code 5.7.57 in Exchange Online.