Mozilla Thunderbird is a free, safe, fast email client that’s easy to use. It has lots of great features including quick message search, customizable views, support for IMAP/POP, RSS support and more. Plus, the portable version leaves no personal information behind on the machine you run it on, so you can take your email and adress book with you wherever you go.
Why do you need an email client? Well, with an email client you can monitor and maintain all your email accounts in one central place. In Thunderbird you can store all access information to all email accounts (e.g. email@example.com and firstname.lastname@example.org) and then choose a master password to access them all.
In addition, you can expand the capabilities of Thunderbird with lots of add-ons. Lightning, a calendar add-on that you can use to remind yourself of upcoming events or to schedule meetings is now already implemented into Thunderbird and does not need to be added manually anymore. Another add-on is FoxClocks which you can use to show the times all around the world in case you need to contact your clients but don’t want to wake them up in the middle of the night.
Available for: Windows, Mac OS X, Linux
Note: If you are already using MS Outlook then you don’t need Thunderbird. Both email clients are suitable to take care of your business needs but Outlook is not for free.