Receiving "550 Please turn on SMTP Authentication in your mail client" when trying to sending email to my zoho email

Receiving "550 Please turn on SMTP Authentication in your mail client" when trying to sending email to my zoho email

Hi Support ,

Earlier i was able to recieve all mails but from two days i m getting below error. If anyone sends mail to our domain email id

info@nexamspro.com

"550 Please turn on SMTP Authentication in your mail client" 


Thanks
Mithun