(rahul.net) anti-junk-email features
Unsolicited junk email is a growing problem on the Internet. Many
users, especially those who maintain web sites or post to Usenet, report
receiving many unsolicited messages a day. Such unsolicited email takes
time and effort to read and delete.
An optional anti-junk-email system called 'Nojunk(tm) filtering' is
available at a2i which is intended to substantially decrease the amount
of incoming junk email that will reach you.
By using, or continuing to use, the Nojunk facility, you are granting
a2i communications permission to (a) examine and analyse junk email that
is diagnosed by the Nojunk facility as probably being junk email,
(b) submit such email to external services such as RSS (see
http://www.mail-abuse.org/rss/ for details), and (c) save such email in
our archives for future analysis or future submission to other external
It is our policy that any such email that we submit to an external
service (a) will be submitted only if a visual inspection verifies that
it is indeed junk email, and (b) will be edited such that a reasonable
attempt is made to hide the identify of the a2i customer for whom the
junk email arrived.
A number of different
strategies are used to together provide an effective shield against
unsolicited junk email. Combinations of these may be used for best
protection against junk email.
- Strategy A: A special address format in Usenet postings that allows
mail delivery only if the destination address is found in a To: or Cc:
line. Otherwise the message bounces with an explanation. Many junk
emailers create lists of addresses and each message is not individually
addressed to the recipient. The use of a Strategy A address in Usenet
postings will cut down your junk email by about 50%.
- Strategy B: A global and/or user-specified list of search patterns.
If a message header matches, the message bounces with an explanation.
We maintain a global list of search patterns that is updated to keep up
with addresses currently in use by the worst junk emailers. Our search
patterns are expected to trap about 60-80% of incoming junk email.
- Strategy C: A special address format encoded based on the Subject:
heading of a Usenet posting. Email replies to the posting are delivered
normally if the Subject: heading is preserved. Otherwise the message
bounces with an explanation. Thus individuals responding to your Usenet
postings can send replies to you normally, but people collecting
addressee en masse and including you in the list will not be able to
send you email, since they are unlikely to save and reuse the original
Subject: heading. The bounced message includes an explanation and also
includes your normal email address.
- Strategy D: A special address format that expires after a specified
time. This lets you use an email address that will exist for a while,
but not forever. This minimizes the possibility of your email address
being archived in places and sticking around indefinitely. Instead,
just decide how long you want your email address to be valid for a given
purpose. For example, if you need to supply your email address when
registering on somebody's web form, and you want them to be able to send
replies in the near future but not benefit from selling it to junk
emailers, use an address that expires in about a month.
Intelligent Bounced Mail
When a mail message is trapped by any of the above anti-junk-email
strategies, an intelligently-formatted bounced message is sent back
which includes an explanation of why the message bounced and how the
sender can retry. Any human sender trying to reach you by email will be
able to see the bounced message and then figure out how to send you
email so it will reach you. Persons sending junk email will not have
the time to analyze bounces, and will simply discard them and not get
through to your mailbox.
User-Settable Nojunk Level
Individual users may set their Nojunk level to between 0 and 10. At
level 0 no filtering is done and all email, including all junk email, is
permitted to get through unhindered. At level 1 only the most active
junk email senders are filtered out. At level 10 junk mail filtering is
very aggressive and will detect and filter out most junk email.
Intermediate levels provide intermediate degrees of protection against
The more advanced features of Nojunk filtering are currently accessible
only from the UNIX shell, but a simple web interface is available to
customers to perform basic Nojunk configuration. You may use 'njdemo'
as the username and password to explore the
Nojunk web interface
in demo mode.
Junk Detection Based on Message Contents
Many experienced junk emailers get short-lived "throwaway" accounts,
send junk email from there, and then move on to other locations. As a
result filtering based on message headers is not always sufficient to
detect junk email. At levels 8 and higher our Nojunk system also scans
message bodies looking for suspicious strings that are often found in
junk email. At level 10 this scan of message bodies is very effective
and will detect most junk email.
Protection from False Hits
At the higher Nojunk levels, detection of junk email is done very
aggressively, so that very little junk email will escape detection. At
the same time, the rate of false hits is probably higher at the higher
Nojunk levels. Users may optionally choose to have junk messages not
bounce but be automatically saved in a separate mail folder in their
home directory where they may be read at low priority from the UNIX
shell. This prevents loss of any email due to a false hit, even though
in practice we find that false hits are very few. Thus users may safely
enable Nojunk filtering at its most effective level 10, without risk of
losing wanted email.
Nojunk(tm) Online Manual
Here is our full online manual "man a2i-nojunk".
To top howto page
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