The conversion channel performs body-part-by-body-part conversions on messages through the MTA. This processing can be done by any site-supplied programs or command procedures. The conversion channel can do such things such as convert text or images from one format to another, scan for viruses, translate languages, and so forth. Various message types of the MTA traffic are selected for conversion, and specific processes and programs can be specified for each type of message body part. If you are looking to use the conversion channel with a virus scanning program, you can either disinfect, hold, or reject messages. A special conversion channel configuration is consulted to choose an appropriate conversion for each body part. For more information, see Chapter 13, Using Predefined Channels, in Sun Java System Messaging Server 6.3 Administration Guide.
Using specialized processing like a conversion channel puts additional load on your system. Be sure to account for it when you plan your sizing strategy.
With the conversion channel, you can use third-party anti-spam and anti-virus software solutions. You can also use the MTA API to create a channel to invoke a remote scanning engine. For more information on the MTA API, see the Sun Java System Messaging Server 6.3 Administration Reference.
In general, it is best that these third-party solutions are shielded from external sites and are only used on back-end or intermediate relays.
The Brightmail solution consists of the Brightmail server and real-time anti-spam and anti-virus (for service providers only) rule updates that are downloaded to your messaging servers. When the Brightmail Logistics and Operations Center (BLOC) receives spam from email probes, operators immediately create appropriate anti-spam rules. These rules are then downloaded to Brightmail customer machines. Similarly, the Symantec Security Response real-time virus rules are also sent from Brightmail. These rules are used by customer’s Brightmail servers to catch spam and viruses.
Messaging Server also supports the use of SpamAssassin, a freeware mail filter used to identify spam. SpamAssassin calculates a score for every message. Scores are calculated by performing a series of tests on message header and body information. Each test either succeeds or fails, and the score is adjusted accordingly. Scores are real numbers and may be positive or negative. Scores that exceed a certain threshold are considered to be spam.
For more information on configuring Brightmail and SpamAssassin for Messaging Server, see Chapter 14, Integrating Spam and Virus Filtering Programs Into Messaging Server, in Sun Java System Messaging Server 6.3 Administration Guide.