It's really sad they dropped Mail support, it was definitely one of the key features of the old Opera.

People defending the feature drop says "today users prefer to use web-based mails", of course they do, they DON'T HAVE AN ALTERNATIVE. A desktop mail client is just a pain and definitely a different concept, you got to install it, run it every time you want to check it, and also they use to be not usables and ugly. So you won't use it unless you are constantly receiving mails from multiple accounts (work or whatever).

Opera Mail was a real alternative to web-based mails, you got your mail client always there, hidden but active, you'll be noticed if any mail arrives, if you wanna access its way more easier to do it than going to gmail and it was CLEAN, it gave you exactly what you wanted with 4-5 customizing options, plus you got it linked to the "mailto:" so you didn't have to worry about that either.