1. Mozilla ThunderbirdThe first and the most popular alternative is Thunderbird, the open-source email client from Mozilla. It is the best when it comes to speed and flexibility. It can expand its usability through plugins and add-ons like Firefox. That’s why most Firefox user will feel easier to work with Thunderbird.
Thunderbird supports all popular protocols including POP, IMAP and SMTP. Another advantage of Thunderbird is that it is available in all platforms while Microsoft Outlook is only available for Windows (and now on Mac OS X too).
One advantage of Thunderbird over Microsoft Outlook which I have personally seen is the use of IMAP. While Microsoft has done some work in this area in Microsoft Outlook 2010, Outlook still tends to hang and become unresponsive if using an IMAP account connection, Thunderbird prospers in this area and works very fast even with IMAP. If you prefer IMAP to access your email, Thunderbird is the best alternative with lots of other features and extensions.
Latest version of Thunderbird can be downloaded from Mozilla Messaging.
2. Zimbra DesktopZimbra Desktop is my personal favorite and I have, as a consultant, recommended and implemented it in many offices. Zimbra collaboration suite is an Open-Source competitor to Microsoft Exchange and Zimbra Desktop is an email client just like Microsoft Outlook. The strongest features of Zimbra Desktop is its ease of use and an elegant user interface. I usually work with IMAP when I’m not using Microsoft Exchange and Zimbra Desktop works like I’m working locally with email, such is the speed of Zimbra Desktop even with IMAP which no one can beat until now.
Zimbra Desktop has an auto-configure feature for Yahoo Mail, Gmail, Hotmail and AOL which makes it a snap to configure an account on Zimbra Desktop if you’re using one of these email services. It also includes a work offline feature which will automatically cache all your email locally so that you will be able to access your email even when you’re offline. This feature works with IMAP protocol which makes Zimbra Desktop the winner in the IMAP usage race.
Another feature of Zimbra Desktop that I like and use a lot is the conversation view. You can view all the email in a single email view like in Yahoo or Hotmail or you can combine the email in a single conversation view which makes it very easy to track and see the conversation going on previously with the same person. This feature is available in Gmail by default.
The new version of Zimbra Desktop also combines the social element with email by providing access to all your social accounts in one place. The supported social platforms include Twitter, Facebook, Digg etc.
Zimbra Desktop can be downloaded from Zimbra website.
3. IncrediMailIncrediMail is rather a fun alternative to Microsoft Outlook. It provides a fun way of sending and checking email by providing a colorful experience. It provides all the features of a standard email client including POP, IMAP and SMTP but in addition to this, provides features like colorful and photo backgrounds while composing emails, email notifiers which are animated characters notifying you about a newly received email, incredibly high quality emotions making your email more attractive and fun.
IncrediMail also includes a feature called PhotoMail Maker which will allow you to add your personal photos as email backgrounds.
One disadvantage of IncrediMail is that it will force you to change your browser homepage and search provider to IncrediMail’s one. If you’re using Internet Explorer 9, it will warn you that some software wants to change your search provider. Just click on “Don’t Change” which will be fine if you don’t want to change your search provider in Internet Explorer.
4. Opera MailIf you’re using Opera as your default browser, Opera Mail provides a very good alternative to any email client as it integrates the mail client right inside the Opera Browser. You can configure Opera Mail easily and there’s no need to open a separate email client. Your email will arrive and show up in Opera browser.
Opera also gives access to offline mail access feature so that you can browse your email even when you’re not connected to the Internet. It also uses a low bandwidth mode which comes in very handy when you’re using a slow Internet connection and especially while travelling. Opera Mail fetches only necessary information on low bandwidth mode.
Opera Mail also integrates a smart spam filter which will block all the spam email. It works in background and doesn’t bother you.
I especially like the organization features of Opera Mail. We can sort the mail the way we want. Getting only unread mail is easier than ever in Opera Mail. While Gmail introduced labels instead of folders, Opera Mail goes a step further by auto-learning feature. Now labels can learn how you interact with them.
Opera browser can be downloaded from Opera website. You can configure mail by going to the menu and selecting Mail and Chat accounts.
5. emClientemClient is another great email client and a competitor to Microsoft Outlook. The new version of emClient has been specifically designed for running on Windows Vista and Windows 7. It is free for home use while you’ll have to pay for the service if you’re a business user. It supports all the popular free email services like Hotmail, Yahoo and Gmail. It can also import settings and email from other email clients like Microsoft Outlook and Mozilla Thunderbird.
I especially like its search feature. It’s very quick and finds anything within the inbox instantly. Other standard features are also included that are by default in Outlook like tagging for messages, signatures and templates, email rules. It even includes translation service directly inside the inbox which makes it very easy to read the mails if you’re getting mails in different languages.
Besides email, emClient supports other collaboration and organization features like Calendaring, Instant messaging, Contacts organization etc. emClient can be downloaded here.
While there are many other alternatives, I have only discussed best five of them in my opinion. You can share your top choices through comments below.