The e-mail reads, in part:

Beginning today, all submissions to the App Store will be reviewed on the latest beta of iPhone OS 3.0. If your app submission is not compatible with iPhone OS 3.0, it will not be approved. Existing apps in the App Store should already run on iPhone OS 3.0 without modification, but you should test your existing apps with iPhone OS 3.0 to ensure there are no compatibility issues. After iPhone OS 3.0 becomes available to customers, any app that is incompatible with iPhone OS 3.0 may be removed from the App Store.

Apple released the fifth beta version of iPhone OS 3.0 to developers on Wednesday. Reports indicate that Apple patched a hole that allowed enterprising hackers to get a preview of iPhone's upcoming multimedia messaging service, which Apple hasn't turned on yet. Another hack that allowed you to enable tethering on the iPhone has also been shut down. There are also reports that YouTube streams over 3G now have higher resolution than before, and that parental controls have been improved.

Apple announced in March that the iPhone 3.0 OS would . The company's will take place from June 8 to June 12, at which Apple could release the software.