Lyris’ low SpamAssassin threshold

via jgc’s newsletter, Lyris’ latest ISP Deliverability Report (Q1 2007) makes an interesting point about legitimate bulk mail and SpamAssassin:

Contrary to popular belief among marketers, message content is not a major cause of deliverability challenges for most email marketers. This finding is a result of testing the content of more than 1,705 unique emails, using [Lyris] EmailAdvisor’s content scoring tool. The content scoring function is based on the content scoring rules of the widely adopted Spam Assassin open source project. The emails tested had an average content point score of 1.04 well below the filter’s generally accepted spam identification level of 3.0 or higher.

Now, that’s broadly good advice — SpamAssassin hasn’t really given much strength to signatures found in message body text in the past couple of years, since the signatures from other sources (especially DNS blocklists and URI blocklists) are much more reliable.

However, note the bit I emphasised. Since when is 3.0 the ‘generally accepted spam identification level’? Only the most paranoid user would ever go that low, since at that level, they’d expect to find 2.22% of their nonspam mail going into the spam folder (according to our own tests). In reality, our recommended level has always been 5.0 points, and that’s what we optimise for. I’m mystified as to where they’re getting 3.0 from…

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  1. Lee Maguire
    Posted June 15, 2007 at 13:16 | Permalink

    My personal filtering is based on whitelists and the SA score, and it looks like I’ve chosen “3” as the cut-off point for where non-whitelisted mail goes into my daily “check me” box.

    Non-whitelisted mail between 3 and X goes into a “probably spam” box for weekly checking. Z to Y goes into a “almost certainly spam”. N is currently about 8, but it gets adjusted to keep some managable level of mail in the “probably” box. (Y+ is either rejected or dropped depending on the connecting server).

    3 was chosen since the highest score a non-spam, non-whitelisted, mail I’ve gotten in the last few years has been just under that. (As far as I know, of course.)

  2. Posted June 15, 2007 at 15:23 | Permalink

    Lee — ok, I take it back about the “paranoid” bit ;)

    Good to hear it works for you — as long as you’re keeping an eye on the “probably-spam” box it should be fine!

  3. Posted June 15, 2007 at 17:57 | Permalink

    I’ve been pushing everything over 2.5 into a “spamy” box for years. At 5 it goes into “zspamy,” and I autodelete at 7.

    I’m pleased to know I’m more paranoid than the most paranoid user. :)