So you just jailbroke and unlocked your iPhone 3G to work with the new 3.0 firmware only to find out that push is not working? Well we have a solution for you. Its not pretty but it works. I know the iPhone-Dev team is hard at working getting it implemented into RedSn0w. But for now here are the steps you need to take in order to get push working on your newly jailbroken iPhone.
First thing you need to do is get a AT&T simcard
Put the AT&T Sim card into your iPhone 3G and restore to firmware 3.0.
You will now have an unactivated iPhone 3G, so you will need to jailbreak it with RedSn0w.
Once that is done you will need to turn of 3G.
Go to settings and turn off your 3G.
You will probably see a waiting for activation message. Just ignore it an open up Cydia.
You should get a “Waiting for activation.” message, dismiss it and Open cydia.
Install all of the updates and then restart Cydia.
Next add the Ultrasn0w source repo666.ultrasn0w.com.The Last o is a number zero.
Let Ultrasn0w install and then turn off your iPhone 3G.
Remove the ATT sim and insert your T-Mobile simcard.
When you turn the iPhone 3G back on you will see the message. “iPhone has been activated” and Push will now be working!