Okay what your problem is from what I can tell is the messages are lagging in the MMS server.(this happened to me)
What I suggest is sending yourself a text message from your phone.
This will force its way through the MMS mail server and in turn push any other messages through be it text or e-mail notifications.
Should only have to do this once and messages should work fine, but if you think they are lagging again just simply text yourself.
hope this helps.