Apple's default Mail app is fine, but many prefer Sparrow because of how much you can do with a swipe and intuitive threading system for messages. While users can get this app on any iPhone, only a jailbroken device can make Sparrow the default option. This means that whenever you tap on someone's email address from another app, it launches Sparrow and not Mail. Sparrow also enables push notifications, so you won't miss a beat every time someone sends you an email.

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