While the stock email app on Android Tablets and Phones is amazing enough, there are many reasons as to why an alternative app is needed. Whatever the case, Android has a large establishment of alternative email apps avilable on its Andorid market. One of those app is the K-9 Mail.
Of all the email apps I have used, this would be hands down the best alternative. Not only is it free, it incorporates and integrates all your email into one application. The app has a similar feel to that of Microsoft Outlook in that all mail from every account is displayed on one huge list.
K-9 is an opensource email client with a design based on the Email application that came with the initial release of Android. It is compatible with most standard email protocol, such as POP3, iMap, and exchange. You can download the application apk straight from the project website or off the Android market.
So, If your looking for the best Android tablet or Android Phone Email app replacement, I highly recommend you use the K9Mail.