M2 is, from version 7 and up, the built-in e-mail client
of the Opera browser
The approach of M2 is rather different from what most of us are used to. One of the major differences between M2 and most regular e-mail clients, is that it has no real folders, only various views and access points to all the messages. Messages can be accessed by
- status (unread, sent, drafts, trash, spam etc.)
- contact (clicking a name in the contacts list will show all messages received from and sent to that contact)
- assigned labels ("to do", "important", "mail back", "valuable", etc.)
- type of attachment (auto recognition)
- mailing lists (ditto, if list headers are properly configured)
- usenet groups
- access points you make yourself by performing a search (all searched are automatically kept as access points, but you can of course choose to delete the ones you don't think you'll need again)
M2 comes with a built-in spam filter that can be set to medium or strong (or switched off). I have found the filter's strong setting very useful, although it is slightly too aggressive and I do need to hit the "not spam" button for a small number of messages daily.
The contact listing is also quite elegant - you can add a photo of your contact, chose a small icon to be displayed next to all messages associated with that contact, add a url so that right-clicking a contact takes you straight to that person's home page, etc.
I should also mentioned the brilliant little trick that you can drag and drop notes from the Opera notes panel to copy the text into e-mail messages.
For all its merits - I am one happy M2 user these days, since I gave up on Ximian's Evolution - the current version has some annoying features which are likely to be bugs. For instance, you can choose whether or not the receivers of your outgoing messages should be automatically saved as contacts, but choosing that the authors of your incoming messages should not be added, is not an option. This is highly annoying for those of us who receive, for instance, a lot of press releases. Also, the "active contacts" in the mail panel and the separate "contacts" panel are not thoroughly synchronized, which means, for one, that you can end up with two different contact listings for the same person. I've also read about people having trouble with creating distribution lists, but I have not tried this myself so far.
I mentioned the "not spam"-button, but strangely, there is no "this is spam"-button, although you can of course modify the spam filter by adding for instance keywords or header types you would like filtered.
Bugs aside, this is the best e-mail client I've ever used. It's wonderfully integrated with my favourite browser, I don't need to keep track of an ever-increasing number of folders, and it saves everything in mbox format so that my e-mail can easily be backed up and/or exported, should something even better come along.
generic-man says: I registered Opera for M2, although its IMAP support is not great (it never deletes messages locally when they're gone from the server, for example)