List-Unsubscribe header

[BasilFawlty]

Hello all,
I am running VB 4.2.3 Patch 2 and have a question about improving anti-spam scores. I use www.mail-tester.com to text emails coming from my site (like when admin sends email to a group of users or all users). My anti-spam score is very good, but there is ONE thing where it says I could improve. When I run a test on emails from my server I get a notice that my email is missing List-Unsubscribe in the header.

I "think" I want to have something like the following in the header of my emails send from my admin account:

mailMessage.Headers.Add("List-Unsubscribe", "<mailto:list@host.com?subject=unsubscribe>");

First, does this look about right and second - WHERE in Bulletin (which script, line, etc) would I place this so that the List-Unsubscribe header is included?

Thanks in advance

--------------- Added [DATE]1495907032[/DATE] at [TIME]1495907032[/TIME] ---------------

Anyone? If someone can just tell me where (in which script and general area in the script) I would look to add an item to header in outbound emails I would greatly appreciate it.