Mail is not outgoing Zoho Mail SMTP

Mail is not outgoing Zoho Mail SMTP

Whenever I try to send an email using zoho mail SMTP, I get this error:
SMTP Error: data not accepted.SMTP server error: DATA END command failed Detail: Email Outgoing Blocked. Learn more. SMTP code: 554 Additional SMTP info: 5.1.8
This is happening from July 28. Before that date, it was working fine. I am using a custom domain email address: support@lishup.com