We are setup as an organization on Zoho mail for more than a week, however the issue persist. Our senders keep getting similar error messages while reaching out to us. Please help, its urgent.

This is the mail system at host us2.outbound.mailhostbox.com.

I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can delete your own text from the attached returned message.

                   The mail system

<harshita@rnt.ai>: host mail.rnt.ai[184.95.38.201] said: 550 5.1.1

    <harshita@rnt.ai>: Recipient address rejected: User unknown in local

    recipient table (in reply to RCPT TO command)