Josh Spector published them. I’ll pluck out a few I like here:
3. If a message was truly urgent, it wouldn’t have been sent to you in an email.
13. You don’t always have to reply.
20. Emails are a terrible place for small talk.
24. Your inbox works for you — not the other way around.
29. The most important sentence in any email is the first one.
34. If you can write one great email, you can get whatever you want.
There are a bunch I disagree with, but I disagree with them in the context of myself. Most of them I get an eh, it depends feeling from. But clearly Josh thinks about this stuff and is sharing what works for him, and that’s the best thing you can do with anything productivity-related, email or otherwise.