Postini's managed services utilize patented pass-through technology versus store-and-forward methods for blocking spam, email-borne viruses, Directory Harvesting and Denial of Service Attacks.

Progent's E-Mail Guard is based on Postini's managed services, which utilize patented pass-through technology versus store-and-forward methods for blocking spam, email-borne viruses, Directory Harvesting and Denial of Service Attacks.

Under Postini's approach, email bound for your email server is processed in real-time through Postini's secure Email Processing Center. Postiniís Connection Manager uses heuristic rules analysis to identify patterns of behavior associated with Directory Harvest Attacks (DHA) and immediately rejects DHA messages. Postini's Content Filter then separates spam and viruses from legitimate messages using an in-memory process that takes only milliseconds. Valid email is instantly passed on to the destination mail server. Email suspected of containing spam or viruses can either be quarantined in a web-based, password-protected message center for review by an administrator or end-user, or tagged and delivered.

Postini's Perimeter Manager Architecture

The entire process is fully automated. Valid email passes through and cannot be physically accessed by any persons other than the recipient.

Postini's system architecture is divided into public and private security zones. The Public Zone processes the flow of email and handles customer web access. Access to the web-based administrative console, for company administrators, or to the message center for end-users, is handled through Secure Sockets Layer (SSL) sessions, an industry-standard public key cryptography methodology for authentication and encryption. Both passwords and data are encrypted before transmission.

The Private Zone is reserved for storing quarantined messages and customer profile and preference information. All user information and user configurations are processed automatically by software. Postini employees do not review this data. Only authorized services are allowed to traverse the two networks, and only authorized personnel are allowed access to the private network.

Glossary of Terms Related to Spam Technology

Term Definition

Data Center

Highly secure, fault-resistant facilities housing customer equipment connected to telecommunications networks. The facilities accommodate Web servers, email servers, switches, routers, modem racks, mass storage and other mission-critical equipment.

Denial of Service Attacks (DoS)

Short for denial-of-service attack, a type of attack on a network that is designed to bring the network to its knees by flooding it with useless traffic.

Directory Harvesting Attacks (DHAs)

Directory Harvest Attacks (DHAs) are scripted attempts designed to steal directory information from unprotected email servers. Spammers send messages with various names to your SMTP mail server until the server recognizes a name and accepts a message. The names from accepted messages are harvested and typically sold to other spammers.

Email Business Continuity Service

A backup email service activated automatically when the enterprise email server becomes unavailable.

Email Perimeter

The outermost edge over which the enterprise has control over an email message before the message is received from or passed to the Internet. Examples are a firewall or a managed service data center.

False Positive

A valid email incorrectly identified as spam.


A system designed to prevent unauthorized Internet users from accessing private networks connected to the Internet, especially intranets. All messages entering or leaving the intranet pass through the firewall, which examines each message and blocks those that do not meet specified security criteria.

Heuristic Rules Analysis

A branch of artificial intelligence whereby expert systems use programs that are self-learning and improve with experience. With spam filtering, the more messages processed the better the results.


See Secure Sockets Layer.

ISO 17799 Specification

ISO 17799 is a code of practice that offers guidelines for information security management. It is meant to provide a high level, general description of the areas currently considered important when initiating, implementing or maintaining information security in an organization.

Load Balancing

In the context of spam filtering, the measured release of messages from a filtering service to an enterprise email server so as not to overload the server. This is an important feature of email business continuity service.

Managed Services

Outsourced IT infrastructure services such as spam and virus filtering.

MX Record

Short for mail exchange record, an entry in a domain name database that identifies the mail server responsible for handling emails for that domain name. For spam filtering to be performed by a managed service at an external data center, the MX record must be redirected to the outsourcer.

Pass-through Filtering

Email filtering done on the fly in memory before being passed on to its intended destination. This is a faster and more secure technique than store-and-forward filtering.

Secure Sockets Layer (SSL)

A protocol for transmitting private documents via the Internet. SSL works by using a private key to encrypt data transferred over the SSL connection. Many Web sites use the protocol to obtain confidential user information, such as credit card numbers. By convention, URLs that require an SSL connection start with https: instead of http.


Short for Simple Mail Transfer Protocol, a protocol for sending email messages between servers. SMTP email servers are the target of Directory Harvest Attacks.


Unwanted or malicious email

Spam Filtering

Also known as spam blocking, the removal of unwanted email before it is delivered to its intended address.


Email filtering performed on a messages stored temporarily on disk. This is slower and less secure than pass-through filtering.

Contact Progent for Email Solutions
If you are interested in using Progent's E-Mail Guard managed services or if you need Progent's consulting services to fix or enhance your email system or help you develop a complete security strategy, call Progent 800-993-9400 or visit Contact Progent.

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