A known rule is that you should never open an attachment which seems suspicious... especially if the attachment is Allenbradleyupdate.zip:
http://www.isssource.com/ransomware-masked-as-rockwell-update/
http://www.isssource.com/ransomware-masked-as-rockwell-update/
Rockwell Automation has learned about the existence of a malicious file called ‘Allenbradleyupdate.zip’ that is being distributed on the Internet. This file is NOT an official update from Rockwell Automation, and we have been informed that this file contains a type of ransomware malware...