This article explains the bounceback error generated by recipient server such as Gmail generating the following code :
552-5.7.0 This message was blocked because its content presents a potential 552-5.7.0 security issue. To review our message content and attachment content 552-5.7.0 guidelines, go to 552 5.7.0 https://support.google.com/mail/?p=BlockedMessage
Email Security.cloud
The error is generated by Gmail (the recipient) which does not allow or accept sending programs , apps because its content presents a potential 552-5.7.0 security issue.
Gmail will not transfer programs or apps especially in parts. Sometimes messages are blocked when you don't include any attachments.This can happen when you include content, images, or links that might share viruses.
We recommend sending any program or file of any kind, by uploading it to Drive and send a link so the other party can download it.