I know it isn't malicious because I own the domain..
You are not the first one to say that ... and then we post the proof

Anyway it is also blocked by Norton

Norton safe web >> https://safeweb.norton.com/report/show?url=netsmart.net.au

IP history >> https://virustotal.com/en/ip-address/27.54.85.177/information/
Many domains on same IP and many are blacklisted

So may be a result of malicious activity on that IP