my email id is logistics1@sarafstone.com. I am getting following error. How to solve it ?

An unknown error has occurred.

Subject 'Kindly provide us booking for Mundra To Dublin  port/Inv. no. 1718/008///2*20/Shipper- Saraf Natural Stone'
Server Error: 550
Server Response: 550 5.4.6 Mail rate exceeded limit
Server: 'smtp.zoho.com'
Windows Live Mail Error ID: 0x800CCC69
Protocol: SMTP
Port: 465
Secure(SSL): Yes