It's still showing not encrypted on the screen which allows all sort of possibilities when done on a browser. For example, let's say you're using Chrome, hard to make sure page contents are not being used somehow.
Which will still see your data unencrypted. And there are open-source browsers too.
In any case, as I said several posts ago, a number of Lavabit customers were complaining about having lost their stored emails; if they were using a desktop email client with IMAP, that wouldn't be the case.