Error: Unable to send message;Reason:553 Relaying disallowed. Invalid Domain

Error: Unable to send message;Reason:553 Relaying disallowed. Invalid Domain

Hi there,

The domain (zecoolinvestment.com) registration lapsed, then was renewed but the MX verification keeps failing.

I have also added the TXT record as you suggested in other topics I read earlier with the details below:

Host - @

Value - zoho-verification=zb11223344.validate.zoho.com

But the MX verification is still failing.

Would appreciate your assistance.

Many thanks!