Comment by dividuum

I've been using mutt for a few years before switching to gmail and finally to FastMail. Once you learn the keyboard shortcuts (https://support.google.com/mail/answer/6594?hl=en or https://www.fastmail.com/help/receive/kbshortcuts.html) I wasn't really slower than using mutt locally. Since they are both single page apps you can't "outrun" them by using shortcuts too fast. It works pretty well for me.