David Wilson has another video up in his series on configuring and using mu4e to handle email from within Emacs. His past videos have already covered the hard parts of configuring mu4e and mbsync. The current video is about using mu4e to compose and send email.
Most of that is straightforward but Wilson also demonstrates how to attach file, save and edit a draft, and cryptographically sign one or all emails. I even learned that you can “directly” compose and send an email without going through the mu4e menu.
If you’re new to mu4e or want to see what using it looks like, Wilson’s video will give you a good overview. The video is just over 42 and a half minutes so you’ll need to set aside some time for it.