Explanation
Trusted Automated Exchange of Intelligence Information (TAXII) is a standard protocol that enables the sharing of cyber threat intelligence between organizations. It allows organizations to automate the exchange of information in a secure and timely manner. References: CompTIA Security+ Certification Exam Objectives -
3.6 Given a scenario, implement secure network architecture concepts. Study Guide: Chapter 4, page 167.

Explanation
SSH is used to securely transfer files to the remote server and is required for SCP to work. Disabling SSH will prevent users from being able to use SCP to transfer files to the server. To enable SSH, the security engineer should modify the SSH configuration file (sshd.conf) and make sure that SSH is enabled. For more information on hardening systems and the security techniques that can be used, refer to the CompTIA Security+ SY0-601 Official Text Book and Resources.

Explanation
PGP (Pretty Good Privacy) is a commonly used encryption method for email communications to secure the sensitive data being sent. It allows for the encryption of the entire message or just the sensitive parts. It would be an appropriate solution in this case as it doesn't require additional infrastructure to implement.