This sort of thing happens to me all the time. People very frequently use "garbage" email addresses (yahoo, hotmail) to order with. When they don't receive order/shipping confirmations because they get bounced back due to "undeliverable, unknown user, account overquota" errors, I get emails from them later asking how come they have never heard from me and want to know their order status. Naturally all my replies get bounced back to me, too... Very frustrating at times...
</rant>
