Symantec Mail Security 6.5 for Microsoft Exchange (SMSMSE) introduces a new performance enhancement feature called Fastpass. This document describes what Fastpass does and how to disable it if you do not want to use this feature.
Fastpass improves Premium AntiSpam performance by skipping a subset of antispam filters for logical connection addresses with a demonstrated history of sending no spam messages. A "pass" is granted to a message source if that source has sent a specified number of consecutive, sampled legitimate messages (25 by default). Once a source has received a pass, the amount of antispam processing that is applied to messages from that source decreases. The number of messages that are permitted to bypass antispam filtering increases as more and more
legitimate email comes from the source. Fastpass reduces the processing time that is required for messages from legitimate sources.
If a message source that has a pass subsequently sends a spam message that is sampled, the pass is immediately revoked. A full antispam analysis is performed on all messages from that source. The source remains eligible to receive another pass, however, by once again meeting all the criteria that is specified in the module configuration.
How Fastpass works
The libfastpass module uses a memory-resident table to store and categorize the message source. IP addresses are granted a pass and those that are currently being evaluated for a possible pass. Fastpass takes some time to build up its effectiveness after it is first enabled. However, Fastpass retains its data across restarts, and the data it collects is persistent across restarts.
The Fastpass table is divided into two parts:
To disable Fastpass
Note: Disabling Fastpass may improve spam detection but will decrease performance.
Detailed information on the fastpass module can be found in the Symantec Brightmail Message Filtering implementation guide: ftp://ftp.symantec.com/public/english_us_canada/products/symantec_brightmail_message_filter/6.1/manuals/sbmf_imp_guide_610.pdf
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