You can customize all the emails and redeem pages that your payees see while redeeming their reward through Ethnio. Ethnio sends the reward emails automatically within seconds of you placing your order. There are multiple emails, depending on the method they choose, and a few different web pages they go through to choose their methods.
We recommend leaving the reply-to as firstname.lastname@example.org so you don't have to hassle with this at all.
One important note: be careful changing the reply-to email address to anything besides email@example.com. We help payees 24/7 with any issues they have choosing methods or getting their rewards, whether it's Amazon Japan or PayPal. The main way they ask questions is by replying to their reward emails, so keep that in mind.