More then a single major feature, Apple introduced a bundle of features aimed to the enterprise, which are…

1. Data Protection: Security enhancements in iPhone OS 4 protect email messages and attachments stored on iPhone 3GS by using the device passcode as an encryption key. New data protection APIs can be used for custom and commercial apps so that business-critical information is protected even if a device is compromised.

2. Mobile Device Management: third-parties will be able to wirelessly configure and update settings, monitor compliance with corporate policies, and even wipe or lock managed iPhone devices.

3. Wireless App Distribution enables enterprises to securely host and wirelessly distribute in-house apps to employees over Wi-Fi and 3G. Apps can be updated without requiring users to connect to their computers.

4. Improved Mail & Exchange Support

5. SSL VPN Support