How To Fix: iPhone "Your SMS mailbox is full." Message
Did you update to iOS 5 and are now experiencing this error message when using your iPhone to send/receive text messages?
“Your SMS mailbox is full. New messages cannot be received until you delete some messages.”
You’re not alone. I learned about this issue from a friend of mine who updated her iPhone 4 to iOS 5 and that message popped up on her screen. At first I thought it was an AT&T issue, but then I learned it was affecting other carriers as well. Next I thought something may have occurred with her backup while updating to iOS 5 due to Apple’s server issues, only then to see someone say they were having the issue on a brand new iPhone 4S after restoring to a backup of their iPhone 4. However, there is an explanation and a fix.
According to an Apple knowledge base article that was posted today, in the update to iOS 5, Apple modified the iOS messaging database and limited it to 15 MB of storage, which is about 75,000 messages in total. I’m not sure exactly why they would do this, but an educated guess leads me to think it had to do with overall iPhone performance.
Nonetheless, to fix your iPhone and start receiving text messages again, delete (all or at least many) message conversation threads by swiping left or right over a conversation and tapping Delete. Then if necessary restart your iPhone and messages should start coming in to your phone again.
It’s a pain, but that’s the fix. If you know of another way to resolve this issue, feel free to leave a comment!