Unfortunately, there's not a lot we can do here.
The browser checks are obviously part of the browser so if they're wrong, we can't do anything about it, though generally it's a good thing if we're both wrong, for consistency 
As for our checks, they are performed in the SwiftMailer library and so there's nothing there we can directly impact. You could report the issues to them directly, but bear in mind that SwiftMailer 6.x is now available so it's possible some of the issues could have been resolved there. We can't use that for the foreseeable future, though, because it requires PHP 7.x.
https://github.com/swiftmailer/swiftmailer/issues
As for the error, that's not exactly intended to be viewed by the end user. It's an error key which can be used to identify a more specific failure reason, if needed, but generally the phrase please_enter_valid_email
is what you should return if the validator returns false.