It seems that the function of delivering offline messages is finally implemented in Google Talk . On the innovations page it is reported that now users can write messages including those contacts who are currently disconnected from the network. Messages will be delivered to them the next time they start GTalk. If they first enter GMail , an offline message will come to them in the form of a letter.
To use this feature, the recipient of the message must use a GMail account, and also enable the function to save historical chats in GMail or GTalk.