Sure - But you just have to do it with two different accounts. Any two email accounts that are regularly attended will be fine. You will have to set them to available or not available as you see fit.
If you use gmail, it's easy to do this with a single email account (but two Warmshowers accounts) using "plus addressing". If your email is email@example.com, you can have one Warmshowers account with firstname.lastname@example.org and another with email@example.com. All email to both will go to firstname.lastname@example.org.