There are better ways to screen contacts outside the organization than being interrupted. Same for marketing messages and announcements. It's important to give different people different abilities, and sort tasks by importance or deadline.
A big chunk of text sent to people is practically spam.
I'm working on a project that improves general productivity (not just developer productivity) with common methods, based on science studies. The methods aren't popular yet.
The biggest insight is that it's far more important to work on big, important problems.