FYI - it also allows you the sender some time to alter the message before its picked up by the reader.
i.e. if you sent but forgot some important piece of info, you can actually go and "edit" your outgoing message before the recipient reads it.
neat feature imho.
"I believe that if life gives you lemons, you should make lemonade... And try to find somebody whose life has given them vodka, and have a party" - Ron White