@Gaby I’m genuinely surprised — 99% of the time I just compose my emails in my email app. On rare occasions, when it’s super important, potentially long and complicated, I’ll compose in my text editor (BBEdit) then copy and paste to the email app for sending. That way I can’t do embarrassing things like Send accidentally or whatever.
@Miraz Under normal circumstances I would used Drafts or perhaps even just the email app. However, with English not being my first language, I am very prone for grammar errors. And having an apl like Ulysses with some revision mode, makes me more confident about what I am writing. At work I use grammarly (the free trier) and also helps.