I have been scratching my head on this one for a while now. We are getting ready to deploy Mountain Lion, and a lot of our users use jabber in iChat in Lion that they will need to use in messages as well. I created a configuration profile to create their jabber account automatically, but I can not figure out how to disable the initial iMessage pop-up that appears the first time you open the messages app for the life of me. It isn't a *huge* deal, but we have iMessage blocked here and it is not approved for use, so I don't want to give the users the change to set it up. Any ideas?