The error message "Heads up! It's unlikely this email will be delivered!" may display when trying to send an email on Greenhouse Recruiting if your email domain is not yet verified.
Your email domain must be verified on Greenhouse Recruiting in order to send emails successfully. Read more here: Email domain verification.
Since Greenhouse Recruiting has not yet been authorized to send emails from your email domain, your emails may not reach its recipient successfully, and the error message may persist until your domain is verified. Your team can take the needed steps to verify your email domain by following the steps outlined here: Email domain verification.