Hmmm...you should be able to keep the display from turning off under settings. I believe that's what turns the wifi off. I'll double check this evening on my 32GB iPod Touch at home.....
But don't you simply receive the email anyway (immediately) when you wake up the Touch(?)
I have Google Voice set up to forward SMS to my MobileMe email address. With this setup I can reply to an SMS using my iPod Touch instead of having to use the inferior keyboard on my phone. The issue I've run into is that the iPod seems to shut off its wifi radio whenever the display is shut off. The only exceptions to this behavior I've noticed are 1) streaming audio apps like Rhapsody continue to work after the screen goes blank, and 2) Push email seems to continue working when the iPod is connected to the charger. I'm sure this is something Apple implemented to preserve battery life, but it sort of defeats the purpose of Push email. Aside from buying one of those expensive cases with a built-in battery, is there a way to force the iPod's wifi to 'always on'?

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