How to restore Apple's 4s SMS to send out a prompt tone?

If you want to delete SMS, plug in mobile phone-file system-library-audio-uisound-delete SentMessage.caf and restart.

If you want to restore the same principle, find a SentMessage.caf file and overwrite it.

Just replace the m4r ringtone in the library/ringtone with ifunbox. For example, you can cut a ringtone casually, convert it into m4r format, and then copy it to your mobile phone to replace the original file and change it in your mobile phone.