We generally use email clients based on personal preferences and habits. However, those that search for improvement often have a daunting task of finding the best email client available. Applications on this page have proven their usability and robustness over the years. Although not necessarily the easiest to use, they provide full emailing power to the most demanding mailers. These are the best email clients currently available:
KMail is a powerful email client for the KDE desktop (Linux) which supports multiple identities, virtual folders, flexible filtering, easy anti-spam and anti-virus integration, calendaring and other PIM features, a rich address book and much much more. Platform: Linux
eM Client is a Windows based Communication Client for managing e-mails, multiple calendars, contacts and tasks. It contains integrated Instant Messaging for Jabber, ICQ and support for Skype with full Communication History. The developers vision is to create an exceptional client application that can compete with MS Outlook, Sametime and GroupWise aggregating Communication platforms, that were never before combined into one unique solution. It is being developed as a user friendly alternative to existing e-mail clients and calendar solutions (MS Outlook, Thunderbird, The Bat!).
Postbox is an email client for OS X and Windows built on Mozilla Thunderbird code. But Postbox is much richer in features compared to Thunderbird, including a number of social features and connections to web services like Twitter, FriendFeed, and Facebook. Postbox indexes your messages, contacts, images, links, and attachments, making it simple to search for items stored in your emails. It comes in two editions, Postbox Express which is free, and the full featured client for $9.95.
Mulberry: Mulberry is probably the most powerful email client around. It has been designed with IMAP in mind, but provides excellent POP support too. It does require some time to get used to, but it is well worth the effort. Cross platform and free.
Thunderbird: Thunderbird is a free open source, cross-platform email client which has quickly gained huge popularity, with a reason. It is extremely easy to use, fairly powerful and robust. Backed by the open source community and having a good extension framework, this is the client that can have it all. Cross platform.
The Bat!: The Bat! was the most powerful email client while POP ruled the world. It is gaining speed on the IMAP side too, but is still way behind others in this list. If you are not too serious about using IMAP, this is probably the best client for you. Platform: Windows
Becky!: Becky! is a fantastic, well thought out email client. It is smart throughout, making your emailing experience faster and enjoyable. Its somewhat fanatical followers are a good sign that once you try it it is not easy to let it go. Platform: Windows