It seems Opera is going to make some major changes in its Operabrowser in coming future, as last month they had announced that they will use new Blink rendering engine instead of Presto and now they had released Opera Mail.
Earlier Opera Mail was integrated into Opera browser and allows you to check mail while browsing internet.
Opera Mail supports all major eMail services like Gmail, AOL, HotMail, Outlook, Yahoo!, Google Apps and all. You can also import settings and profile from your existing email clients like Mozilla Thunderbird, Outlook, Windows Live Mail and so on.
It supports all major email protocols such as POP3, IMAP and SMTP. Opera mail is available for Windows and Mac.
The main thing is that Opera Mail comes with Low Bandwidth Mode which tries to use as little as possible bandwidth of yours. Let say if you enable this feature then it will not fetch more than 100 lines of message until requested by you, and it will also fetch only new messages and will not fetch their attachments until requested by you.