Relaying Disallowed when sending to Zoho Mail

Relaying Disallowed when sending to Zoho Mail

Please Help.

I have a new zoho business account (gabrielmethod.com). I have verified the domain within zoho control panel and configured the mx records on my host site to point to zoho (this has been working as a redirection to a Zimbra account so I know that my host is capable of this).

When I send a mail to my account at gabrielmethod.com from an external email client to test I get an error from zoho mail system reading : host mx.zohomail.com[72.5.230.114] said: 553 Relaying
    disallowed (in reply to RCPT TO command)



I am keen to start using my zoho mail so please advise.