[thelist] Spam filters

Tue Sep 14 15:40:03 CDT 2004

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From: "Jason Handby" Date: Tue, 14 Sep 2004 14:33:41 +0100
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Subject: [thelist] Spam filters
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X-Virus-Scanned: by Quik Internet spam & virus firewall at quik.co.nz
X-Barracuda-Spam-Score: 0.2
X-Barracuda-Spam-Status: No, SCORE=0.2 using per-user scores of
TAG_LEVEL=2.0 QUARANTINE_LEVEL=5.0 KILL_LEVEL=5.0 tests=BAYES_40,
DRUGS_ERECTILE
X-Barracuda-Spam-Report: Code version 2.63, rules version 2.1.280
 Rule breakdown below pts        rule name                      description
 ---- ---------------------- -------------------------------------------
 -0.00 BAYES_40               BODY: Bayesian spam probability is 40 to 44%
                            [score: 0.4394]
 0.22 DRUGS_ERECTILE         Refers to an erectile drug

Hi all,

I have been working on a website which allows people to register and then
search a database according to various criteria. Once the user has finished
searching, the site emails them a detailed report on their search results
that they can refer back to. This email is formatted as HTML.

Recently the client has noticed that they are having more problems with
emails being blocked by users SPAM filters and not getting through. We know
that the email is not SPAM, but clearly it looks like SPAM as far as (at
least some) filters are concerned.

Do any of you have any general suggestions / guiding principles for creating
emails that don't look like SPAM? Are HTML emails more likely to cause
problems than plain-text ones? Does the length of the email matter? Are
there any key phrases we should be avoiding? (We're not selling Viagra :-) )

Any experiences / suggestions / links to resources would be gratefully
received.
========

A few off the top of my head:

HTML email is more likely to trigger spam filters if:
- it has large fonts
- it has capitalised links, eg "CLICK HERE"
- image content outweighs text content

and of course the usual phrases whether plain or html email

Note that some commentators claim that up to 20% of "legitimate" emails are
being caught be spam filters, but it really depends at what level the "kill"
level is set at..........

Another example that came through tagged as spam:
====
X-ASG-Orig-Subj: Bodega Gigs
Subject: [SPAM]Bodega Gigs
To:
MIME-version: 1.0
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X-Barracuda-Spam-Score: -4.4
X-Barracuda-Spam-Status: No, SCORE=-4.4 using per-user scores of
TAG_LEVEL=2.0 QUARANTINE_LEVEL=5.0 KILL_LEVEL=5.0 tests=BAYES_00,
HTML_80_90, HTML_FONT_BIG, HTML_MESSAGE, UPPERCASE_25_50
X-Barracuda-Spam-Report: Code version 2.63, rules version 2.1.259
 Rule breakdown below pts        rule name                      description
 ---- ---------------------- -------------------------------------------
 0.00 HTML_80_90             BODY: Message is 80% to 90% HTML
 0.01 HTML_MESSAGE           BODY: HTML included in message
 0.28 HTML_FONT_BIG          BODY: HTML has a big font
 -4.90 BAYES_00               BODY: Bayesian spam probability is 0 to 1%
                            [score: 0.0000]
 0.26 UPPERCASE_25_50        message body is 25-50% uppercase

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