Opera Mail is a stand alone e-mail client for Windows and OSX created by the Opera team.
Ranked in these QuestionsQuestion Ranking
Pro Automagic smart filtering
After a bit of use Opera learns what e-mail belongs in what folder just by previous usage. This makes for a convenient way to have e-mails filtered without having to manually mange every e-mail.
Pro Free and based on Mozilla code
Opera Mail is completely free to download and use and it is based on Mozilla's code, which is what makes it a bit similar to Thunderbird in looks and function.
Pro Intuitive user interface
The design of the UI in Opera Mail is clean and intuitive, making for an easy to use client.
Con Sync is slow
Opera tends to be slower on e-mail sync when compared to other popular clients.
Con Can not be set as the default email client in Windows 8-10
There is no current way to set Opera Mail as the default email client for Windows 8 through 10. This makes it difficult to open files that would normally open in the client.