Overview

When sending messages to Microsoft SMTP servers, the email is not going through with the following Non-delivery receipt (NDR):

The following organization rejected your message: <Server>
Diagnostic information for administrators:
Remote Server returned '550 5.7.0 Message Size Violation'

This error might be caused because the email size is bigger than what is set in the SMTP Security options. The size limit of the incoming message delivered via SMTP can be also changed for performance optimization.

Solution

1. In the Kerio Connect administration interface, go to Configuration > SMT server > the Security Options tab.
2. Select the Limit maximum incoming SMTP message size to option.
   
   

   Note: the default value is 10 MB.

3. Specify the maximum size of incoming messages.
4. Click Apply.

Testing

The specified limit for incoming messages via SMTP reflects in the mail SMTP settings. NDR rejections are no longer received.