"Email Security.cloud" is a product working in combination with "Symantec Messaging Gateway" as part of a range of services offered by Broadcom, headquartered in California. It features spam filtering, firewall protection, and block lists with resource guides of detailed troubleshooting steps for email delivery. Additionally, a legitimate email which has been incorrectly given a verdict of spam can be submitted to Symantec for analysis and filter review.
smtp;553 Message filtered. Refer to the Troubleshooting page at http://www.symanteccloud.com/troubleshooting for more information. (#5.7.1)