The relays utilize two layers of protection against spam: reputation filtering and anti-spam filters.
The Proofpoint Dynamic Reputation service (PDR) is a cloud-based engine that identifies suspicious email senders and stop incoming spam at the connection level or rate limit the senders. This technology eliminates 83% of incoming spam.
There are many rules that are considered for deciding whether it is likely that any given message is spam or not. Powered by patent-pending Proofpoint MLX machine learning technology, Proofpoint Spam Detection solution examines and filters millions of possible spam attributes in every email -- including message envelope headers and structure, email images, email sender reputation as well as unstructured content in the message body -- to prevent spam emails, attachment-based spam (including PDF and image-based spam), while automatically filtering and adapting to new spam attacks as they appear.
The relays' email spam prevention and protection solution is automatically kept up-to-date via Proofpoint's cloud-based Dynamic Update Service, ensuring maximum email spam detection and protection at all times.
Proofpoint Spam Detection solution is an anti-spam filter that is multi-lingual and offers outstanding accuracy and protection against spam emails in any language, including hard-to-analyze, multi-byte character languages such as Japanese and Chinese.
Messages with a spam score equal to or greater than 50 will be quarantined. The spam quarantine is https://devnull.tamu.edu.
The spam quarantine provided by Proofpoint is a self-service system which provides end-users with their own safe holding area for spam messages and a Web or email-based interface for end-users to access emails flagged by the appliances, as well as the ability to configure personal safe- and block-lists.
A usedful Web site for information on this topic is IT Security's documentation on spam.