That link does not work for me either.
And just to be clear, I find the button labeled Community - Advanced Email Settings in TroopTrack Settings under Edit Troop Settings.
Click the button and you get a 404 in the Community section.
And the button is trying to link to https://community.trooptrack.com/t/4228.
I just figured it out, you have to be logged into the Community for the link to work, mine always did because I am always logged into the Community. I tried in a private window and get the error then logged in and the same link works.
The article is now public no more 404 errors, @JohnTseng thanks for helping to troubleshoot that one, can be difficult when access levels come into play.