An agent from the European Union Delegation in a third country must share a confidential report on recent diplomatic negotiations with a colleague from the European Commission who is based in Brussels. The agent needs to send this file securely, ensuring that only the recipient can read it and that the integrity of the document has not been compromised during transmission. Considering the best practices in cybersecurity and the EU's data protection principles, what is the most appropriate action to ensure the security of this confidential information exchange?