The early sales success of the iPhone is fuelling speculation that there could be a business role for the device.

Watchers such as analyst Gartner have warned that using the iPhone for corporate email could present security issues but, with over 700,000 units already shipped, the device’s unique capabilities and user demand could prompt Apple to release a business version.

Some US firms are already reporting demand from users for iPhone support as a way to unify voice, email, internet and entertainment access. In response, banking giant Bear Stearns last month warned staff that the iPhone will not hook up to corporate servers.

But Apple chief executive Steve Jobs has said some firms are already running pilots hooking up to Microsoft Exchange and other mail servers.

Experts said that unless Apple strikes a deal with Microsoft for its ActiveSync synchronisation software, the iPhone is likely to be a second-class citizen on Exchange networks, relying on web mail and lacking push email and security features.

Keni Barwick, mobile developer at integrator Conchango, noted that the latest Exchange update improved Mac support. “I wouldn’t be surprised if Microsoft licensed ActiveSync to Apple. It’s recognition that the user experience on the phone is as important as on the desktop.”

Visto also recently announced Visto Mobile for the iPhone, supporting both Exchange and Lotus Domino via the Imap protocol and using SSL encryption. Apple could also persuade RIM or a similar provider to bolster its email credentials.