Not able to receive emails

Not able to receive emails

My email was working fine for last 3 months. Now suddenly whenever someone sends an email they get an error:

The response from the remote server was:

550 No Such User Here


Final-Recipient: rfc822;  ram@wsquare.work
Action: failed
Status: 5.0.0
Remote-MTA: dns;  wsquare.work . (103.21.59.21, the server for the domain  wsquare.work .)
Diagnostic-Code: smtp; 550 No Such User Here
Last-Attempt-Date: Tue, 14 Mar 2017 05:09:08 -0700 (PDT)