Aquamail has an unbelievable amount of customization that you can do. So much customization in fact that it seems to be too much.
It's a really good email app with its only major flaw being that it doesn't do as perfect a job formatting the messages as the GMAIL and stock SAMSUNG mail apps do. This is a problem that the software's author has been struggling with to fix.
One of the big things that drove me away from the Samsung stock mail app was the fact I could not have my email automatically check itself every minute. That's important to me. And yes, I can manually check for new mail as often as I want, but I need to do it without taking it out of my pocket or holster. An audible alert lets me know when new email has arrived.
Trust me, I have sampled all the popular mail clients and Aqua Mail seems to be the most feature-enriched.