Google has apparently added the ability to send offline messages to Google Talk users. This is absolutely awesome and it has been a feature I have wanted in an instant messenger for a long long time. I’ve only been using Google Talk for the past year so I’m not sure if another messenger service has gotten this feature, but as far as I know this is the first?
The What’s New page for Google Talk says that this is a new feature. It looks like you need to have Chat History enabled in order for this to work:
If your friend is offline, you can still send chats for them to receive the next time they log in. Just click on their name in your Google Talk Friends list and send your message from the chat window – your message will appear the next time they log in to Talk.
If your friend signs in to their Gmail account before signing in to Talk, they’ll see your chat as an unread message in their Inbox.
Note that offline messages can only be sent to users with Gmail addresses, and who have not disabled chat history in their account. If you were chatting off the record before your friend went offline, you’ll need to select Stop chatting off the record before sending offline messages.
This is just another reason why you should try to get people to open a GMail account instead of just using Google Talk with any email address. I can’t wait to see this in action but all of my friends are online. 
News Source: Googling Google
I know windows live messenger haves had off-line Messaging for along time and I think it was put WLM 8.0
ICQ have had this feature for as long as I can remember.
I’ve seen the offline message feature in [skype.com] too.
I didn’t know about Skype and ICQ, but I could have sworn that WLM didn’t have the offline messaging feature.
when will it be able to connect to aim, yahoo, etc???
I am sure that is a feature they are actively working on, since they say they are [tech.cybernetnews.com]
Yahoo! Messenger has had this for years!!!
In Y!, when someone is offline just IM as if they’re there and when they return they’ll see “Offline Messages” (even if message archiving is turned off). If you’ve got a mic, you can even call and leave free voice-mail.
Why Y! messenger is largely ignored, I have yet to figure out. For me, Yahoo! has the best everything.
RE the cross-compatibility between Google talk, aim, and Y!… Yahoo! is compatible with Windows Live msgr, so it’s certainly a possible feature if the co’s work together on it.
BTW did you notice Gmail’s dead?
Gmail typically only goes down for a specific set of accounts at one time. For instance, if I have troubles accessing my email my friends probably won’t. It is probably all dependent at what data center your email account is located at. The outages normally don’t last more than 15 minutes from what I have experienced, but it always happens when you need it.