Seems to work okay for me

Read the reviews, figured I would take a chance for 99 cents. Within 2 minutes, I was already using it as a replacement for my iPhone mail. I have had no crashes, and love the ability to add sub-folders and sort email. Storing up to 1000 messages is a bonus as well. 200 messages is just not enough. Several other nice features, but those 2 were the reasons I wanted this, and am quite happy.

Torque3k about ibisMail - Filtering Mail