We can configure DLP policy so that it doesn't monitor the emails that send to the internal users.

Think about such scenario: the confidential docs can be send to the internal users for reviewing, but, these docs cannot be send to the outside of the company, or, should be encrypted before hand out.

Here are the steps:

1. Open a existing policy that should not create incident for internal users.

2. Under 'Detection' tab, click 'Add Exception' button:

3. Select 'Protocol or Endpoint Monitoring' under 'Protocol':

4. Choose 'Email/SMTP' under 'Protocol', on the 'Also Match' list, choose 'Recipient Matches Pattern':

5. Under 'Matches Pattern' section, in the 'Recipient Pattern' box, input the name of the internal email domain:

Note: there should be an '@' added before the domain name.

6. Finally, the policy should be look like this: