If you are a heavy user of email you'll love Mail Enhancer Pro, an amendment to the native Mail application IOS.

Mail Enhancer Pro allows you to check emails in the inbox by color also adds a menu to view our unread messages quickly, options for marking messages as read / unread with a gesture, different signatures for each email account, full support for HTML, rules, customizing notifications, filters, etc..

You can download for $ 4.99 in Cydia, somewhat expensive but worth it, you'll find BigBoss repo. You need to have jailbroken your device.