OK, so this have been driving me crazy. Every now and then I'll type an email, and the word doesn't sometimes gets flagged by the spell check. I thought maybe I was using the wrong apostrophe, but that's not it. I've tried typing doesnt and letting spell check correct it to doesn't . It will accept that, and then subsequent doesn'ts seem to be OK. This is mostly in Mail that I notice this behavior. Here's a little collection of doesn'ts for you.