A reader in the UK contacted me with an interesting question: How would you find a text message from a particular date several months back — without having to reload page after page of previous messages on the iPhone?
The answer is to access the backup of all your text messages, stored on your computer after you sync the iPhone through iTunes. This OS X Daily article explains the process of accessing your backup file — not easy, but do-able. If this is something you need to do regularly and want easier access, you might want to check out the program Decipher TextMessage.
(You can also get easy access to old voicemails using Decipher Voicemail).
Karen Anderson
iPhone 4 Tips 