emails sent to me bounce back as: domain non-existent

emails sent to me bounce back as: domain non-existent

I have a zoho mail email address, and i can send emails but cannot receive any for some reason.  When I try to send an email to my zoho account from another address, it bounces back and says that it's undeliverable: nonexistent domain.  However, my domain clearly does exist and I can send emails from my zoho account to other email addresses.  What is going on?  How do I fix it?