I'm a fan of email.
Everyone tells you that email is the reason why you are unproductive. That same people, however try to sell you the next instant messenger as the "solution" to the mental overload of having thousands of mails in your inbox. Most of these tools, though, only work with horribly fat, closed clients that need your immediate attention 100% of the time. There's no labeling, sorting, or starring of messages. There's no good way to communicate in batches. IMHO, Messaging has its place, but it's not a replacement for email.
Email, on the other hand, is the mature tool that silently helps you get stuff done. I'm a fan of email.
Also, I have always been a fan of Fastmail. While I'm currently not a customer (I was at two different occasions), I applaud the team's drive to keep the worlds email infrastructure as open as possible.
Mail is one of the last uses of the Internet, where open standards still matter and JMAP sounds like the next step in the right direction to keep it like this.