Per practising what I preach, I've switched my mail clients to using GnuPG signing by default, or have at least started on switching them - main work machine done, laptop and home Windows PC to go.
One of my complaints about email is that it's difficult to verify the sender or the contents, but I don't do anything to help people receiving my email to do so.
Plus, it started making more sense to me some time ago, protecting myself from people who might misquote me in order to cause harm to me professionally.
It's not perfection, but it's a start. My one bitch is Thunderbird/Enigmail will remember my passphrase for an arbitrary amount of time, but can't be set to clear when the screensaver comes on, for instance. I poked about at gpg-agent, but couldn't find any frontend for MacOS that seems to do that.