Need help :Message not transmitted DLP Email Prevent SMTP_MESSAGE.5300

Hi,

We use DLP in our company, we have problem with email prevent showing on the log that a message is not transmitted.  we have an Error on the log :

SMTP_MESSAGE.5300 Error while processing

I have found a link below talking about this, but i didn’t understand where to put configuration? MTA or in our DLP prevent mail server. And which configuration do i have to add ?

https://support.symantec.com/us/en/article.tech219387.html

https://support.symantec.com/us/en/article.tech219387.html

Best regards