Enable Sync to mobile for Google Mail Hosted domains…:
Remember, if you use google mail “hosted” for your domains, and want push syncing to your iPhone, etc you need to enable the sync to mobile button on the management screen to enable push of calendar, email and address book entries.
If you use Gmail by itself, the syncing to mobile is already enabled. Which is what they should have done with hosted domains, as well.
More here: www.google.com/support/mobile/bin/answer.py?answer=138740…