Inbox overflow leads to less colleague contact

For this reason companies, such as U.S. Cellular, Deloitte and Intel have a ‘no e-mail Friday’. This does not seem to be a structural solution, others say, because now everyone sending more e-mail on Monday to Thursday. Anyway it’s a good signal to the employees.
Others say there should be an e-mail code of conduct. (Within R&D 20 colleagues defined such a code of conduct in a workshop some time ago.)
What do you think? Is this article also representative for your company too? Are you too longing for more live contact with colleagues? Do you have experience with a ‘no e-mail Friday’ or a code of conduct? Do they work?