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SpamAssassin is a spam advisory system that CIS runs on the
mail servers. It uses statistical methods to detect messages
that are likely to be spam, applying hundreds of patterns and
functions to each message that passes into WHOI's email system.
When it detects a potential spam message, it marks up the message's
headers so that your mail client software can filter it.
SpamAssassin does not delete or reject any messages. Because
it is less predictable than the spam
blocking methods we use,
we leave it up to you, the email user, whether to make use of
its information or not. By configuring your mail software to
filter based on the headers SpamAssassin adds, you can reduce
the amount of spam you have to see.
Each pattern that SpamAssassin checks for has a weight associated
with it -- a small number which indicates how likely it is that
a message matching that pattern is spam. For instance, messages
containing the word "VIAGRA" might get 2 points, whereas
messages sent using software commonly used to send spam might
get 0.5 points. Weights can also be negative, meaning that a
message is likely not to be spam; mail sent using legitimate
mailing-list software such as Mailman and Majordomo gets negative
points. If the total number of points for a message meets or
exceeds 5.0, the message is marked as spam.
Using SpamAssassin in Thunderbird or Mozilla
SpamAssassin adds several headers to messages it determines resemble
spam. By using your email client's Message Filters facility, you
can sort these messages into a separate folder from your inbox
automatically. (We do not recommend deleting these messages outright,
because SpamAssassin is not perfect.) The headers that SpamAssassin
adds include the following:
- X-Spam-Flag: Yes
- X-Spam-Level: ***** (The number of stars
is equal to the number of points the message got.)
Here's how to sort spammy messages into a separate folder. The
process is a little long, but you only have to do it once.
- Open your email client.
- Create the new folder. Right-click
(or Control-click, on Macintosh) on the Inbox folder. A menu
will pop up; select
the option New Subfolder... Name
the folder "filtered-spam" or some such.
- Open Message Filters. From the Tools
menu, select Message Filters... A window will
pop up. If you already have some filters, they will be displayed.
- Create a filter.
Click the New... button, located on the right-hand side of
the window. A new window will appear. Here's what to do in
- In the Filter Name text box, give the filter a name
- In the Filter Criteria section, pull down the menu
that says "sender",
and select Customize Headers. In the box that pops up, click New,
and type X-Spam-Flag. Press Enter, then click OK.
- On the right-hand
side of the Filter Criteria, there is a text box. Type Yes in this box.
- In the Filter Action section, pull down the
menu that says "Inbox" and
change it to the name of your new folder (such as "filtered-spam".)
As you receive new messages in your inbox, your email client
will automatically test them for SpamAssassin's X-Spam-Flag
header. If the value of this header is Yes on a given message,
the message will be automatically shunted into the "filtered-spam"
folder. Check this folder at least once a week to make sure nothing
legitimate has been accidentally filed as spam.