Hi,
The simple answer is you can't.
In Messages menu > Preferences > General Section there is a line about "When I Quit, Set my Status to Off Line".
When this is ticked all accounts will not accept Off line or wake up calls.
Not all Jabber servers do Off Line IMs.
Also if it was delivered to another device the account was not Off line.
If the general Setting above is NOT set then the IMAgent app "Listens" in the background when the Mac is On and Awake.
Then if an iMessage or an AIM message is received then the app will start up (of it's own accord) so that you can deal with it.
AIM have a setting you can change at a On line page about whether your AIM or AIM valid name will accept Off line IMs See https://settings.aim.com/
You can log in to this page with an @mac.com Apple ID but not the iCloud issued @me.com or @icloud.com names. (AIM registered names work)
This is because Apple have iChat 6 and Messages doing two Logins, one to AIM and another to me.com
This then allows the AIM servers to Verify the password.
The page I linked does not have the capacity to do a dula Login to verify a password.
(It also means that iCloud issued names will not work in iChat 5 or earlier)
You can use a Jabber app such as Psi that has a Service Discovery part to it which in most cases will tell you if the server is doing Off LIne IMs and Conferences and File Sharing and allow you to sign up for Transports and other "features"
However using it on the Google servers tell you nothing. (It's not clear what they actually offer)
Summary.
AIM do Offline IMs
If you have the right sort of AIM valid or AIM name you can turn this ON or Off at AIM web pages.
The iChat and Messages app have a setting for not receiving "Wake up calls" if the app is Quit but the Computer is On.
Not all Jabber store Messages for Off line Delivery.
However if you have other Logins you are not Off line.
There is no Syncing with other services.
9:32 PM Friday; February 22, 2013
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.2)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images." No, Seriously
