I have been searching for a way to make my google hosted e-mail to “push” via MobileME. I found this tip on Mac OSX Hints Page.
You can set up MobileMe to use any email address as a ‘push’ email on the iPhone. The first thing you need to do is set your non-MobileMe (.Mac) email address for auto-forward to your MobileMe (.Mac) account. When you create the email account, make sure you set it up as Other (not as a .Mac or MobileMe account.) Then select IMAP as the type of account. Enter the name and auto-forwarded email address. (This is the email address that will show as the [...]