From Eden Shochat:
one key thing missing for me is how to be able to get an alert for urgent emails so that you don't feel like you might be dropping the ball, which in turn will make you check email more often than you should. my personal mechanism is that starred messages are sent as notifications, and behind the scenes i have some logic that decides which messages to star. it might be an overkill to most people, but simple examples to do with gmail are:
hard-coded family / portfolio / key contacts
specific subjects/message body keywords that at that point in time should be considered important. a deal you are working on or a trip you are planning.
of course if you use zapier/etc then you can have a speadsheet instead of hard-coded, etc.
secondary issue is "social contracts" that we spoke about. if you only read email 3 times a day, you should tell people about it to avoid missed expectations. might be out of scope for the article.