I’m a little confused by the wording of your query.
Are you asking this question as a developer of compliance-enforcement software?
Are you asking as someone who needs to implement a solution and you are looking for software names or configuration information?
General directions to go in (since I’m not sure what you’re looking for) would be:
Email transfers of attachments are a possibility.
When you say “URL filtering” do you mean outgoing web requests?
Or do you mean outsiders probing your web servers for confidential data?
If you reply (to everyone, not just me) with more details about what you’re looking for we (as a group) may be better able to help you.