what's the difference between mairix and NotMuch?

suddenly I have all kinds of "mairix" stuff interrupting my #emacs workflow. It's in org and it's in Gnus. What in the world is this? I found http://www.rpcurnow.force9.co.uk/mairix/, which leads me to ask -- what's the difference between mairix and NotMuch?

Probably notmuch.

Mairix hasn’t been updated in five years, so it’s probably safe to ignore it and just use notmuch for everything (since notmuch is regularly updated).

I believe I experienced this error due to using the Straight.el example to include contrib since orgmode refactored it recently. This included the org mairix stuff. I fixed it as follows: I found and customized =org-link-parameters= to no longer include the Mairix lines, which were probably created when I included all the contrib with straight. The problem is gone now. By the way, it would be nice if there were a compliment to =org-add-link-type= like =org-remove-link-type=. I was surprised to have one but not the other.