a2i (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 services.

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.

Nojunk(tm) Strategies

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.

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 junk email.

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".

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