Graymail services provide users with the option to unsubscribe from unwanted marketing emails, reducing inbox clutter from legitimate but unwanted mass mailings.

Defanging a URL means modifying it so that it is not clickable and cannot be directly accessed by a user, but still retains the visible structure of the original URL. This allows users to see the URL for informational purposes without being able to click on it and potentially open a malicious site.
Common defanging methods include replacing certain characters (like "." with "[dot]" or "http" with
"hxxp") to render the URL non-functional while keeping it recognizable.

Non-final actions are actions that do not terminate the message filter evaluation, such as adding headers, setting variables, logging, etc. Final actions are actions that end the message filter evaluation and determine the fate of the message, such as accept, drop, bounce, quarantine, etc.
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

How to Encrypt SMTP Conversations using TLS:
Step 1
Obtain an X.509 certificate and private key from a recognized certificate authority.
https://www.cisco.com/c/en/us/td/docs/security/esa/esa14-0/user_guide/b_ESA_Admin_Guide_14-0/b_ESA_Admin_Guide_12_1_chapter_011001.html?bookSearch=true