How to check a message BEFORE the server in Outlook?

Question

C++ / C#

Given: corporate mail network, messaging through Autluk. Sometimes, users manage to send personal data to each other, which unnecessarily excites the Security Service. Currently, messages are checked for the content of PD in them on the server side (hence, already after the user has pressed the "send" button, so, if anything happens, the user will definitely "arrive"). I would like to ban messages based on the content of keywords in them already on the user's side. Ie: the user clicked "send" -> the script ran through the message (including attachments) -> in case of some problem, it displayed the "Alert" window. Further - at the user's own risk.
Question: what is the easiest way to implement such a thing? VBA? C++? How to view attachments (most of all, excel and pdf are of interest, in which the text is saved, ocr is not needed)?

Answer 1

If you are not embarrassed by the development of a plug-in for Outlook
https://docs.microsoft.com/en-us/visualstudio/vsto...
Any average programmer can do it.
The most difficult thing is perhaps the list of STOP words