They differ a lot. Email is more like a letter and is a killer app unto itself, chat has proven to be a thing that gets bolted on to something else. No chat client to date has ever been able to stand alone, and none of the early leaders ever amounted to anything.
Hell, Yahoo had entire verticals like ocean shipping self organizing around Yahoo Chat back in the day and never figured out how to monetize. Slack is going to be another salesforce widget.
I don't understand what you're saying. They're both asynchronous delivery of written messages. There are no length limits on either. There are no technical differences between them.
And they're both monetized exactly the same way, as part of a more comprehensive suite of office productivity offerings. People don't pay for Yahoo Chat the exact same way they don't pay for Yahoo Mail.
Sure there is. Email is an open standard, enabled by other other open standards. Things like authentication and service location are dictated by implementation. As a user, I can email anyone on the planet and retain those communications. My employer retains some email dating as far back as 1992, in native format.
Chat is almost always a closed loop. There are usually large implementations, and as a user I can only message within one. There are some exceptions to that. Chat always gets kicked around as corporate strategy changes. At work, I’ve probably used a dozen incompatible Microsoft solutions as their strategy meandered around. Jabber was the big attempt to make chat like email, and it failed.
Email still runs the world, despite its many flaws.
Email is a set of standards, sure. Instant messaging is a concept. Email is an implementation of that concept. There is already an open standard for instant messaging; it's email.
Hell, Yahoo had entire verticals like ocean shipping self organizing around Yahoo Chat back in the day and never figured out how to monetize. Slack is going to be another salesforce widget.