I keep receiving this error during sending email from my gmail account (which i set my zoho mail as POP3 in my gmail)
Delivery to the following recipient failed permanently:
<email address>
Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the server for the recipient domain
synergy-group.com.my by
mx.zoho.com. [74.201.155.125].
The error that the other server returned was:
554 5.2.3 MailPolicy violation Error delivering to mailboxes