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Opera Mail, internally referred to as M2, is the e-mail and news client built into the Opera internet suite. Its interface is somewhat different from many other e-mail clients in order to provide better integration into the Opera internet suite. It has spam filtering (both automated and learning, i.e. Bayesian), supports POP3 and IMAP, newsgroups as well as Atom and RSS feeds.
Opera Mail uses one database that keeps an index of all mail, and sorts the messages automatically into several 'views' or accesspoints. Messages are automatically sorted by type, such as mailing lists, and mail with attachments . This approach to indexing allows for quicker access to messages. For instance, a message sent to a mailing list with a word document attached will appear in both the Documents attachment view and in the Mailing lists view. M2 can also use Bayesian filtering to automatically sort messages into other views. All messages in the database are accessed by opening the Received view.
The Opera Mail component also provides a contact manager and simple IRC client. The IRC client allows the user to connect to multiple servers at a time. It is possible to chat in private and to transfer files between users. The chat rooms appearance can be modified by modifying a CSS file (demonstration).
Opera Mail can display text and HTML e-mails and uses the layout engine Presto of Opera to display HTML.
With the release of Opera 9.5, Opera Mail featured a new backend to increase speed and extend IMAP support.
As of Opera 10, it includes message composing with rich text support and inline spell checking.