Advanced users might notice that the "full headers" of mail you receive through our Web hosting service include headers named X-Spam-Status, X-Spam-Level, X-Spam-Flag and X-Spam-Report.
These headers are unrelated to our spam filter system that blocks most spam messages. The headers are added by a separate scanner called SpamAssassin that examines all incoming messages that make it past the spam filter.
On this page:
SpamAssassin looks at the actual content of each message and assigns it a "spam level" score based on how much it "looks like" spam; for example, messages that mention "Viagra" will receive a higher score than messages that don't.
Unlike the spam filter, SpamAssassin never blocks any mail directly — it merely adds the special headers to each message. The headers don't affect anything, and are usually invisible unless you show the "full Internet headers" in your mail program. If you're an advanced user, you can probably create rules in your mail program to sort mail that receives high SpamAssassin scores. For example, our Webmail system and Microsoft Outlook (but curiously not Outlook Express) allow you to create rules based on message headers.
Here are some sample "headers" from a spam message:
X-Spam-Status: Yes, hits=9.0 tagged_above=-999.0 required=7.0 tests=FORGED_RCVD_NET_HELO, FORGED_YAHOO_RCVD, HTML_20_30, HTML_IMAGE_ONLY_04, HTML_MESSAGE, HTML_WEB_BUGS, NO_RDNS_DOTCOM_HELO X-Spam-Level: ********* X-Spam-Flag: YES X-Spam-Report: SpamAssassin headers added by tigertech.net. Test details: * 0.6 HTML_WEB_BUGS BODY: Image tag intended to identify you * 0.5 HTML_20_30 BODY: Message is 20% to 30% HTML * 1.5 HTML_IMAGE_ONLY_04 BODY: HTML: images with 200-400 bytes of words * 3.0 NO_RDNS_DOTCOM_HELO Host HELO'd as a big ISP, but had no rDNS * 3.0 FORGED_RCVD_NET_HELO Host HELO'd using the wrong IP network * 0.5 FORGED_YAHOO_RCVD 'From' yahoo.com does not match 'Received' headers
This message received a SpamAssassin score of 9 because of the six different reasons shown in the "details" lines. The details are often technical: in this case, most of the score was due to the spammer's computer impersonating Yahoo.com, for example. In our experience, a message with a score of 7 or more is almost always spam, so one option you might want to consider, if your mail program allows it, is to add a rule that looks for messages that contain at least seven asterisks in the "X-Spam-Level:" header and files them in a "Spam" folder.
You can use the SpamAssassin scores to filter probable spam using our Webmail system.
First of all, create a folder called something like "Spam" if you haven't already done so:
Then add a filtering rule:
X-Spam-Level: *******". It should look like the picture below.This rule will make Webmail examine any new messages to see if they have a SpamAssassin score of 7 or more (because those messages have seven or more asterisks in a "X-Spam-Level" header). If you want to make it more sensitive, you could use fewer asterisks in the rule (but that may lead to more "false positives").
Remember that SpamAssassin isn't 100% perfect (see the next section for details about that), so be sure to glance at the contents of the "Spam" folder every so often.
Unfortunately not. SpamAssassin is fairly accurate in identifying spam that makes it past our blocking filters — probably about 99% accurate — but it's not perfect. It can misidentify borderline messages that "look like" spam but really aren't, such as messages from friends sending Viagra jokes, or messages containing legitimate information about prescription drugs, or messages in which the sender's mail server had some sort of technical configuration problem that made it appear that it was "forging" someone else's domain name.
As a real-world example, SpamAssassin will add 1.5 points to the score of a message that includes the words "life insurance" in the subject. That's because most messages that say "life insurance" in the subject are spam, even though a few aren't. 1.5 points isn't enough for a message to be considered "spam" by itself, but it's remotely possible that an unlucky combination of several such things can give a perfectly innocent message a high SpamAssassin score.
Because of that, we don't block such mail, and most people will want to at least glance at the sender and subject of each message before deleting them. People usually filter SpamAssassin-tagged messages into a "Spam" folder of their mail program, where they can look through them if they suspect they're missing a legitimate message.
For more information about SpamAssassin, including descriptions of what a high score actually means, see the SpamAssassin Web site.