DLP (Data Loss Prevention) is a security service that is configured only through an outgoing mail policy on Cisco ESA. DLP allows Cisco ESA to scan outgoing messages for sensitive or confidential data, such as credit card numbers, social security numbers, health records, etc., and apply appropriate actions, such as encrypt, quarantine, notify, etc., to prevent data leakage or loss.
https://www.cisco.com/c/en/us/td/docs/security/esa/esa11-0/user_guide_fs/b_ESA_Admin_Guide_11_0/b_ESA_Admin_Guide_chapter_01001.html

To provision the configured encryption profile with the Cisco Registered Envelope Service, the engineer must use the provision command as shown in the menu options of the exhibit.

DKIM public keys are published in the DNS using TXT records as specified by RFC 6376. The recipient's mail server uses the selector and domain to look up this TXT record and retrieve the public key for signature verification.

Message Filters Subcommands.
set: Sets filter to active or inactive state. For more information, see Creating a New Message Filter.
For Example, using the filter -> set subcommand.
https://www.cisco.com/c/en/us/td/docs/security/esa/esa11-1/user_guide/b_ESA_Admin_Guide_11_1/b_ESA_Admin_Guide_chapter_01000.html?bookSear ch=true