Receive email from another zoho email fine, but can't receive from other external emails.

Receive email from another zoho email fine, but can't receive from other external emails.

I can send mails to all external emails but I cannot receive from any other externals. I get such error:
The response from the remote server was:

554 5.7.1 <info@popmall.store>: Relay access denied

Final-Recipient: rfc822; info@popmall.store
Action: failed
Status: 5.7.1
Remote-MTA: dns; mx.popmall.store. (185.27.132.238, the server for the domain popmall.store.)
Diagnostic-Code: smtp; 554 5.7.1 <info@popmall.store>: Relay access denied
Last-Attempt-Date: Mon, 11 Sep 2017 20:26:13 -0700 (PDT)

However, I can send and receive emails within my domain emails. I have my DNS over at Cloudflare.