Great guide but there seems to be a typo/mistake regarding how to save the smtp password in step 2/gmail: should use sendemail.smtpPass instead of the non existing sendemail.password.
Good catch! Want a chance to try out your email skills and send a fix to ~sircmpwn/public-inbox@lists.sr.ht? The git repo is here: https://git.sr.ht/~sircmpwn/git-send-email.io. If you're not interested, I'll push the fix, but figured I'd give you a chance to get credit for it.