Flexmail 4.1 is just about the only other email client worth looking into IMO.
http://www.pocketinformant.com/produ....php?p_id=mail&
The only issue with Flexmail is that new message indicators in the Win 6.5 Titanium panels, SPB Mobile shell, and others that are written for the standard Pocket Outlook mail client don't update.
Other than that, I personally think that Flexmail is great, however, I don't use it anymore because I miss not having the new mail indicators. I just suck it up and use Pocket Outlook.
I've read a lot on the Flexmail forums for solutions to the indicator updates in SPB Mobile shell, Titanium, etc. and the Flexmail people don't seem too interested in making the indicators work.
Hope this helps.