In Apple’s eyes, there’s probably no better email client than their own. But that hasn’t stopped others from trying, and one of the more popular Mac attempts is Sparrow, which has now taken an even bolder leap from the desktop to the iPhone and iPod touch.

The Verge is reporting that the highly anticipated Sparrow email app for iOS has hit the App Store at long last, the culmination of many challenges for the French developer of the same name. While there are any number of third-party email clients on the Mac -- from heavyweights like Microsoft and all the way down the food chain -- doing the same on iOS proved more difficult than first expected.

Much like the company’s popular Mac client, Sparrow for iOS borrows inspiration from developer Loren Brichter, whose Tweetie app eventually became the official Twitter app. That makes for a much better-looking email client than Apple’s own, but creates problems for third-party developers.

"Apple doesn't like to be dependent on third party applications,” explains Sparrow developer Dominique Leca, who heads up a small team of engineers. “Apple's Mail app didn't work well with Gmail for a long time because it wasn't relying on Google's label APIs," noting that end users are the ones who ultimately suffer from this.

Unfortunately, Sparrow arrives in the App Store a bit less full-featured than originally hoped: There’s no POP support, but sadly there’s no push email, either. The developers had initially found a way to do it using what’s known as the “VoIP Privilege,” a method used by apps like Skype for listening in the background for incoming calls or chats. The only potential workaround to this situation is for Sparrow to use its own email servers, but it’s not something the company wants to tackle due to security risks.

The company’s only hope appears to be persuading Apple to add an API specifically aimed at push email apps, something that Leca is attempting to gain support for with an online petition, which readers can participate in by entering their email address on the Sparrow website.

In the meantime, Sparrow for iPhone has arrived -- the 9.0MB app is available now from the App Store for $2.99 and works with all devices running iOS 5.0 or later (but sadly, is not universal for the iPad at this time).

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