Everyone from Microsoft to Nokia has tried to kill Research In Motion's BlackBerry smartphone platform. But after almost four years of nonstop effort, BlackBerry is still on top. Not even a massive lawsuit from holding company NTP managed to slow down BlackBerry in the eyes of the business world. In fact, since then, BlackBerry has expanded beyond the world of the corporate enterprise into the SMB market and even to consumers. Why is BlackBerry so successful?Personally, while I like some BlackBerry devices (I really love the design of the Pearl), I have never been the biggest fan of the platform. In fact, I don't really have a favorite when it comes to mobile e-mail. I like aspects of different systems, including those from Intellisync (now Nokia) and Good. I even liked a mobile version of Eudora I tried a few years ago. Each platform has distinct advantages and drawbacks. None of them is, in my opinion, definitive.

But for most business users (and a growing number of consumers), BlackBerry is the gold standard for mobile e-mail. Regardless of whether its BlackBerry Enterprise Server or BlackBerry Connect, most North Americans (and an increasing number of Europeans) think BlackBerry when they think mobile e-mail.

Here are my five reasons why I think BlackBerry is still the king of mobile e-mail.

5. Carriers like the BlackBerry. What, you say? Why would carriers like BlackBerry? Don't they always complain about the "RIM tax"? Well, they do, but they also like to collect revenue. And BlackBerry devices sell contracts.

In terms of the technology, the system is efficient when it comes to use of bandwidth. What does this mean? It means that end users don't pay as much for mobile data while BlackBerry devices don't hog a lot bandwidth on the carrier's end. There are more than 200 carriers who offer some form of BlackBerry service around the world.

4. Device management is included with the BlackBerry Enterprise Server. IT policy control is a big reason BlackBerry wins. IT managers need total control over what their employees are able to do with a wireless device. BES can manage mobile devices and that's important.

3. Security is locked down. BlackBerry Enterprise Server is highly secure. Unlike a lot of other push e-mail offerings, BlackBerry doesn't require outbound ports to be opened on an enterprise's firewall to operate. For many verticals, such as government agencies or financial services, this kind of security is essential.

2. BlackBerry is comprehensive. The biggest challenge all of BlackBerry's rivals face is the comprehensive nature of RIM's solution. BlackBerry isn't just a device. It's not just middleware. It's not just security. It's not just device management It's all of the above. Yes, it's expensive, but it delivers on all aspects.

1. BlackBerry is easy to use. For most end users, BlackBerry delivers a great user experience across its devices and for both enterprise and personal accounts. BlackBerry does what it says it does, and it's relatively easy to set up.

So there it is. If you want to knock BlackBerry off the top, you need to be able to do all of these things better and cheaper than BlackBerry. Good luck.