iPhone users (and ex-iPhone users) attempting to sign out of Apple's iMessage service recently began running into a nasty bug. Signing out of iMessage means that iPhones trying to text your number should seamlessly switch back to using SMS. However, this hasn't been happening lately—instead, these iMessages continue to be sent as iMessages. They never actually make it to their destination, and neither the sender nor the receiver is given any indication that the message has failed.

Apple acknowledged the bug in a statement to Re/code this morning, noting that it has "recently fixed a server-side iMessage bug which was causing an issue for some users," and that an additional software update was being planned to fix more problems.

Signing out of the iMessage service has always been more difficult than enabling it, and I say that as someone who recently disabled iMessage to make jumping between iOS, Android, Windows Phone, and other mobile operating systems easier. In my case, iMessages sent to my newly disconnected number would simply fail to send, and the problem only worked itself out after I changed my Apple ID password (thereby signing all of my devices out of the service), disassociating my phone number from my Apple ID, and then calling Apple support about the problem. This new bug sounds worse, since message senders don't even know that the texts aren't arriving at their destination.

It's not clear whether the promised software update will be applied server-side or if it will require an update to iDevices and Macs. We'll continue to follow the situation as it progresses.