I just picked up an iPhone 4 with iOS 5 installed and was able to sync all my 3GS content into the 4 except email accounts. I had backed it up in my computer off the 3GS but it won't let me check the "Sync Mail Accounts" box in iTunes...help?
The email account must also exist on your computer via outlook etc for it to sync. The only thing that really gets synced is the account information and settings. The mail itself does not sync. Probably a lot easier to manually enter your account info on the phone and pull your mail down from the server.