smtp;541 5.4.1 Mail rejected by destination domain

smtp;541 5.4.1 Mail rejected by destination domain

Hi,

We have an SMTP server on our office network to allow scanners in our office to do Scan-To-Email.  It has been working fine for the past couple weeks but ever since last week mail stopped coming in from scanner with the following error:

Reporting-MTA: dns;mail2.zacway.com
Received-From-MTA: dns;iptarget
Arrival-Date: Tue, 20 Sep 2016 20:25:10 +0800

Final-Recipient: rfc822; desmond.chen@zacway.com
Action: failed
Status: 5.4.1
Diagnostic-Code: smtp;541 5.4.1 Mail rejected by destination domain

Could you please help with our concern?

Thanks,
Desmond