encrypt outgoing messages in the exchange server

[abdulrahman al-badi]

dears

I am not expert in exchange and i need help from you in this case 

we use exchange server and we got incident that one of outgoing messages get compromised . 

whats your ideas to encrypt the outgoing from server side ?

any proper - post - guideline for setup the outgoing encryption  ?

so i can refer it to the tech person as he is new and our expert just left before the incident  

[#2]

There are various types of encryption available, read this document and choose the one best suited for your scenario: https://docs.microsoft.com/en-us/office365/securitycompliance/email-encryption