SMTP Error: data not accepted

SMTP Error: data not accepted

Hi Team

I am getting below error on my site. 

SMTP Error: data not accepted.SMTP server error: DATA END command failed Detail: Mail rate exceeded limit. Use the link mail.zoho.com/UnblockMe to unblock SMTP code: 550 Additional SMTP info: 5.4.6

Can you please check? Seems like my account has been block. Can you please resolve ASAP?

Thanks