How can I improve performance of my GMS Anti-Spam content filtering?
I have activated some of the GMS Anti-Spam filtering options, and performance of my mail server seems to have suffered as a result. How can I improve this?
When you activate the filters in GMS Anti-Spam, the amount of processing that your server has to do is increased. If for example, you have a large Restricted words file, this file will be checked against each line of an email message that arrives.
When a message is MIME encoded, attachments will make up a large portion of a message, but these too will be checked for restricted content.
If we take a normal message with a 2MB attachment as an example, we would expect the message to have around 50 – 100 lines of message text, followed by a further 40,000 lines of encoded attachment text. This means that the Restricted words filter is checked against over 40,000 lines of text, even though the encoded attachment is unlikely to contain anything that you would want to block.
The impact on performance is therefore due to scanning parts of messages which it is not necessary to scan. To improve this, go to the GMS Anti-Spam interface, and select Content->Restricted Words, then set the Search Mode to be the first xxx lines, where xxx is the number of lines that you want to scan. A figure between 50 and 300 is reasonable.
Making this change will improve performance of the Restricted word filter by a considerable amount.
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