No instant e-mail notifications using Yahoo mail android app

[#1]

I have installed the Yahoo mail ndroid app and the e-mail is good. However I can only get instant e-mail notifivations when on wifi. I can pick up emails on 3G but only by opening up the inbox. The emails still do not show up as notifications. Anybody any idea what is going wrong and how I can fix it? No reply so far from Yahoo technical help.

[Johan]

Do you get notifications from the preloaded messaging applications in the phone? Or is it just this Yahoo app that does not give any notification?

[#3]

I get notifications from the other preloaded email  when they are opened up. SE technical help line said this afternoon that the Xperia phones do not support push email other than Gmail. I think that is poor!