Email are probably the easiest ways that information can leak on the organization. Microsoft Office 365 has data loss prevention (DLP) policies definitely subscription levels that, if arranged properly, may also help prevent data leakage. Assuming you have an E3 or E5 license, you possibly can set policies and show tips reminding users that they can shouldn't be sending sensitive information.
If you already can tell your users make shouldn't be emailing information such as credit card numbers, social security numbers and also other sensitive identity information, the reality is that people will forget and email information regardless. By creating a DLP policy that proactively searches for this sensitive information and blocks the transmission, you are able to it safer either way your firm and recipients of this email.
To do DLP rules, first decide if you are using a specific preexisting rule set or if you need to make any. Go to the Office 365 Security & Compliance page and membership with administrator privileges. Just go to "Data loss prevention" thereafter click on "Policy".