Previously Airbnb hosts could contact guests through the email alias feature, which created an unique and anonymous email for guests — something like jane-rstykk@guest.airbnb.com. Now this option is no longer available to hosts by default.

For privacy reasons the email link has been removed https://www.airbnb.com/resources/hosting-homes/a/an-update-for-hosts-who-use-the-guest-email-feature-195

However, from a computer hosts can reactivate email option thorough this section https://www.airbnb.com/account-settings/professional-hosting If you don't have access to the Professional hosting tools you can activate it here https://www.airbnb.com/users/settings