In apple mail, usually I just typed a few words in the search box, and that will find what I need.
As an example : some text here
and then I choose the sub category = “subject contains:”
The results set did include extra emails that did not exactly Match my text request.
So to effectivley change the request from “subject contains” to “subject equals”, I simply enclosed the search text in quotes like :
“some text here”
And it seems that created an exact match (the same way it does when searching at google)
Just in case this is helpful - Dave