Set up a compliance BCC email to automatically copy each outgoing email to a compliance email address. Check enable, enter the compliance BCC email address for your organization, and click Save.
Step 1 : Go to Setup
Step 2 : Enter BCC
Step 3 : Select
Step 4 : Check enable
Step 5 : Enter the compliance BCC email address for your organization
This blog is very useful to learn about Compliance BCC Email setup.