Unusual sending activity detected when sending email

Unusual sending activity detected when sending email

I am getting an error when my application tries to send an email via a specific zoho email account. I use this email account to send emails on specific events such as account creation, account approved, post approved and stuff liked that.

The error i get is '550 5.4.6 Unusual sending activity detected. <a href=https://www.zoho.com/mail/help/usage-policy.html target=_blank>Learn more.</a> Use the link mail.zoho.com/UnblockMe to unblock'

What is this error message and what does it mean? Can it be avoided? IS there anything i can do ?