Users will be able to get mail on the PlayBook directly from a BES (BlackBerry Enterprise Server) only after a software update coming later this year, said Jeff McDowell, senior vice president of enterprise and platform marketing, at a panel discussion Wednesday at the CTIA Wireless trade show in Orlando.

Messages from any other e-mail system with a Web interface, including Microsoft's Outlook Web Access, will be able to go directly to the PlayBook as soon as it ships, McDowell said. Users will be able to log into a VPN (virtual private network) to access enterprise e-mail securely through Web clients.

A Wi-Fi-only version of the device is scheduled to go on sale at Best Buy and other retailers on April 19. A spokesman for Sprint, which has announced it will sell a 4G version of the PlayBook, declined on Thursday to give a ship date for that product.

RIM has developed an advanced tethering system for the PlayBook and BlackBerry that can be controlled via policies set by enterprise IT departments. For example, when the PlayBook is moved a certain distance away from the BlackBerry, tethering can be automatically terminated and no data from the phone will remain on the tablet. Multiple employees in a company could even share a PlayBook, each tethering their own BlackBerry to the tablet at different times, with no trace left of the other users, according to McDowell.

RIM has a lot riding on the PlayBook, which is up against stiff competition from the popular Apple iPad and dozens of tablets based on the Android OS. The upcoming device, announced last year, has had a mixed reception from industry analysts and from developers. RIM shares some concerns from the developer community about ease of app development for the tablet and is working to address them, McDowell said.