[TimTheTinker]

> What sort of features does a mail client need though?

How about a consistent, reliable implementation of modern web standards? If you had to write a mail client in Java, would you rather target Java 1.5 or the most recent version?

Many small (and large) features together make a huge difference when it all adds up to providing an implementation of modern web standards that is consistent with other browsers and with modern standards. It's a huge burden to always be checking "is this supported in IE11 or is there a polyfill we can use" when wanting to use a native function or object (not to mention features that can't be polyfilled or transpiled, like ES6 proxies).

[Crinus]

It might sound like i am trying to be a contrarian, but Java for me is a special case and actually i'd probably stick with Java 1.5 or even 1.4 which was the last Java that i liked (i always liked the idea of Java as a very simple OO language and i disliked it when it started getting extra baggage - useful baggage to some, but still it deviated from the simplicity). But really that is a case of personal taste. If you replaced Java with some other language, like -say- Go, i'd most likely go with the latest version (...although again Go 2 does sound like it might follow Java's trajectory, so who knows, but for now i'd use the latest one).

But honestly i'm not a fan of requiring the latest version of something just for developer convenience. It might have to do with growing up using outdated computers for years and seeing most programs not work or work slowly/badly, often without a good technical reason (outside programmer preference).