Issue Sending & Receiving Emails

Hello - We recently created a new email address for our account but have been unsuccessful at sending or receiving emails using this webmail site (https://emailmg.homestead.com/roundcube/) or from Outlook.  Here's the message we're receiving when we try to send an email to the office@ email address that we setup on your site.  Sorry, we were unable to deliver your message to the following address.  <office@riverbreezecampground.com>  Recipient address rejected: undeliverable address: host fr-int-smtpin7.hostinger.io[private/dovecot-lmtp] said: 550 5.1.1 <office@riverbreezecampground.com> User doesn't exist: office@riverbreezecampground.com (in reply to RCPT TO command)