Postbox Express is based on the premium version of Postbox but with a lot less features. Some of them include:
search history suggestions conversation view simplified account & folder views status update to Facebook & Twitter support for POP, IMAP & RSS easy account setup wizard anti-phishing & malware services add-ons 
Bear in mind though, Postbox Express is no longer under active development and the last shipping version is 1.01. Apart from that this software does use some major CPU resources when sending or receiving emails so it's no good for low-end systems.That said, if you'd like to use a different, sexy yet functional email client, Postbox Express is worth a try. This software looks awesome on Mac OS and not too shabby in Windows. Get Postbox Express here.
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