A good idea but there are cheaper alternatives.
Platform: iPad, iPhone
Mail Pilot is an email client for iOS that's designed to transform the email inbox into a easily managed to-do list.
Messages in your inbox are flagged as incomplete so that you can deal with each one individually. Send a reply or mark it as spam and then simply hit the complete button to archive messages when you are finished.
Using the app there are also other details which can be added to mail such as dates, which enables you to save themand go back at a later date. You can also combine related mail from multiple sources into lists, which can be extremely helpful when managing notifications from social networking sites, newsletters and other less pressing mail.
Although originally intended as a subscription-based service, Mail Pilot’s developers have since decided to launch the app for £10.49 with no subscription.