I'm running for gmail accounts, and three hotmail accounts. The only problem I had was setting up the Gmail accounts through the Gmail setup process on the iPhone. When I did, I didn't have push or any kind of notifications unless I manually checked the mail every time I opened the email client. The solution that I found through the google support website was to set up the accounts under the Exchange settings on the iPhone. After I did that, everything pushed exactly as it should and worked great.