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Anti-SPAM Services
Mainstream offers anti-SPAM filtering for all e-mail that is hosted at
Mainstream. This means that any e-mail that is picked up by our
clients using imap, pop or via our Web-based interface can be
filtered.
The filtering is performed on the e-mail as it is received. It is
examined, using techniques described below, and can be flagged in the
subject line, moved to a different folder (only supported for our imap
clients), or deleted.
A record of all in-bound e-mail, who it was from, what the subject
was, and if it was considered SPAM can be kept and sent to you on a
periodic basis. This allows for examination of logs to see if a piece
of e-mail was accidently disguarded.
Each piece of e-mail is assigned a SPAM score. This score is based
upon matches against databases, key words, or other heuristics applied
against the e-mail.
The SPAM score threshold that is used to consider a piece of e-mail
SPAM can be adjusted. It can be set so that very few pieces of SPAM
make it through the filters, but some valid e-mail may be considered
SPAM. It can also be set so that some SPAM makes it through, but
valid pieces of e-mail are rarely considered SPAM. There are also
multiple settings inbetween.
Speak to your Mainstream rep to find out more about anti-SPAM
filtering.
Anti-SPAM Techniques
The SPAM-identification tactics used include:
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Header Analysis: SPAMmers use a number of tricks to mask
their identities, fool you into thinking they've sent a valid
mail, or fool you into thinking you must have subscribed at some
stage.
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Text Analysis: SPAM mails often have a characteristic
style, and some characteristic disclaimers and CYA
text.
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Blacklists: Use many blacklists, such as mail-abuse.org,
ordb.org or others. These lists identify known SPAMmers.
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Razor: Razor is a collaborative SPAM-tracking database,
which works by taking a signature of SPAM messages. Since SPAM
typically operates by sending an identical message to hundreds
of people, Razor short-circuits this by allowing the first
person to receive a SPAM to add it to the database -- at which
point everyone else will automatically block it.
Once identified, the mail can then be optionally tagged as SPAM for
later filtering using the user's own mail user-agent application. The
system can also be configured to automatically remove SPAM, or to
place SPAM into a special folder for later review.
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