I've been using Apple Mail since the OS X Public Beta in 2000. Its address completion and rich text support are entwined in how I think about authoring emails,

I've been using Apple Mail since the OS X Public Beta in 2000. Its address completion and rich text support are entwined in how I think about authoring emails, so I'm simply more comfortable using it for that purpose. It also helps that Emacs-style movement keys work throughout OS X, including Apple Mail's "new message" windows. I did give mu4e a go, i.e. for writing emails, and I never got to a point where it really appealed to me. I do love it, though, for reading and managing my tens of thousands of email messages. It's also nice that I can easily create links to messages in mu4e, which I can include in my org-mode files.