I have 3 separate email accounts and my email notifications do not show up when the screen is locked (btw upgrated to IOS6). Here is how I got my email notifications to work in locked screen node:
go to Notifications>changed all 3 email notification options to (alert style = none, show preview = off, view in lock screen = off)
back to Notifications>changed 1 email account at a time back on to ((alert style = banners, show preview = on, view in lock screen = on).
Not sure if it matters, but I had Badge App Icon = off.
Hope this helps.
