iOS users on Apple's official community support forums are reporting that the iMessage functionality is seeing sporadic outages, despite messages appearing to be sent. The source of the problem is currently unknown.

As SMS messages are being sent unhindered, the problem could be with Apple's servers. That remains unconfirmed, however, and Apple is yet to comment on the issue.

The status page for iCloud, which covers iMessage, says that the service is online, Mail aside. The latter was "slow or unavailable" according to Apple, though normal service now should have resumed.

iMessages was introduced in iOS 5 as a way for iOS users to send free messages across iPhones, iPods, and iPads, since the latter two devices do not send text messages due to the lack of phone functionality. The service drew comparisons to BlackBerry Messenger, a killer feature for the RIM device. Previously, users would have to download an app like WhatsApp, which allows users to send message across platforms provided that both users have the app installed. iMessage works only on iOS devices.

The latest version of iOS, iOS 6, is available for general download on Sept. 19. It launches on Apple's iPhone 5 this Friday, Sept. 21.