Linux has a number of email clients available, but we still have to give the "best" medal to the feature-filled, extensible Thunderbird.
- Supports multiple POP and IMAP accounts for all your email addresses
- Easy account setup with the account wizard
- Powerful, yet simple-to-use search and filtering
- Saved searches
- Multiple viewing options, including vertical columns
- Message threading and conversation views
- One-click address book adding
- Attachment reminders
- Tabbed message viewing
- Message archiving, perfect for Gmail users
- Built-in junk filtering
- A migration assistant that helps you move your accounts from other email clients like Outlook
- An open source add-on infrastructure that lets you customise Thunderbird for your needs
- Integration with the GNOME desktop on many distributions, including Ubuntu
Thunderbird may not seem like much out of the box, but apart from its small, convenient features -- tabbed browsing, multiple layouts, and a pseudo-conversation view, to name a few -- you can install a lot of different add-ons to customise it to your liking. Where many mail clients aim to be like Outlook and provide an all-around, sometimes bloated organisation app, Thunderbird lets you build up from the more basic email client to make it however big (or small) you want. For example, you can import address books and Outlook PST files, or skin it to look like Apple Mail. It also has a very powerful search feature, and Mozilla's new rapid release cycle is pretty nice too.
Thunderbird doesn't have many downsides these days. It used to be that if you wanted better integration with your desktop, you'd have to turn to something like Evolution, but Thunderbird has recently taken over as the main email client in a number of distributions, including Ubuntu, meaning it plays very nicely with the desktop. Really, since Thunderbird is so customisable, it's hard to have any complaints.
Evolution was long the main competitor to Thunderbird, and while it's a good program, Thunderbird ousting it as the default Ubuntu client has made it pretty unnecessary. If you want an all-in-one email and calendar solution, Evolution might be worth a look, since Lightning (Thunderbird's calendar add-on) isn't necessarily the best around. Other than that, it's still a good client which performs well, has some useful add-ons, and an OK interface; it's just that Thunderbird does all these things a little bit better in our opinion. Still, it's definitely worth a look, especially if you're using a distribution that still integrates Evolution with the desktop.
KMail is a popular option for those using the KDE desktop, and while it has some niceties, it's also pretty buggy in my experience. Its big advantage is that it integrates very well with the KDE desktop and other KDE programs, so if you're knee-deep in the KDE desktop, it might be worth a shot -- but Thunderbird should serve you pretty well too.
Lastly, while it isn't the most feature-filled on the block, Claws Mail is super lightweight and fast without being feature-bare. It has a pretty configurable interface, a few plugins for RSS, calendar, and other things, and is the perfect companion to a lightweight desktop like LXDE. It isn't quite as polished as something like Thunderbird or Evolution, but it'll get the job done.
These are some of the better, more popular options, but if you use a different desktop email client (or a non-desktop client, which can be just as great), let us know which one you use and why in the comments.
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