Default permission rules
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Default Permission Rules  
     
ChoiceMail comes with several email permission rules already installed. These rules are helpful in eliminating spam messages as they are, but you can also use them as models to create your own permission rules.  
 
Note: All permission rules created by DigiPortal Software begin with a '$.'  
 
$Remove ADV: emails  
Theoretically, advertisements are supposed to start with 'ADV' in the Subject field. For those that helpfully do, this permission rule detects and deletes these messages.  
 
$Stuff after end of HTML page  
A legitimate HTML message ends with the </HTML> tag, but spammers often add extra random characters after that tag to try and break systems that look for duplicate messages. This permission rule looks for messages with extra characters after the </HTML> tag – these messages are almost certain to be spam.  
 
$URLs with email portion  
This permission rule detects the trick where spammers try to hide the REAL server by using an "@" character in the URL, preceded by a character string that typically looks like a well-known web server address. For example: http://www.ibm.com@somenastyserver.com.  
 
$Bogus postmaster message  
This permission rule detects spammers who try to break through by pretending to be the postmaster at some website.  
 
$Bad words in body  
This permission rule is included as a sample rule, showing how to detect objectionable words in the body of the message. (This writer doesn't know too many bad words and so extending this rule is left as an exercise for the user. J)  
 
$Images with webbugs  
Web bugs are essentially image URLs that contain arguments such that, when you try to view the image, the server processes the arguments. Web bug arguments are often unique to each recipient, which lets the spammer know who actually looked at a message. This permission rule deletes messages that contain web bugs.  
 
$HTTP as argument  
A favorite trick of spammers is to use a well-known server, such as Yahoo, to redirect you to a spamming site. This permission rule detects messages using this trick.  
 
$Masked URL prefix  
This permission rule detects attempts by spammers to disguise a URL.  
 
$Words split by bogus HTML tags  
Spammers try to break up words by using fake HTML tags that are ignored by your browser. Their goal is to disguise words like VIAGRA by writing them as  
V<x>I<ddd>A<ssdsd>G<qw>R<fdf>A.  
This permission rule doesn't try to decode the actual word – it simply deletes any message that contains this kind of sequence.  
 
$BODY tag before HTML  
This permission rule detects any attempt by spammers to send a message with incorrectly formatted HTML tags.  
 
$URL with digit portion or %  
This permission rule detects URLs that are raw IP addresses.  
 
$Drugs  
This permission rule detects email messages with a few well known drugs in the Subject field. Use this as an example of how to detect drugs or other objectionable items.  
 
$Anti-Bayesian detector  
Spammers break through Bayesian filters by including large numbers of random words in a message so that a Bayesian filter cannot leverage history to determine whether the message is spam. This permission rule detects random words in a message.  
 
$Empty body and subject  
This permission rule deletes empty messages. Sometimes there are ONLY attachments in these messages, and people you don't know should not be sending you attachments.  
 
$Domain Address Check  
This permission rule invokes the domain-checking system that examines the body of a message, extracts server names, looks them up, and determines whether the actual IP addresses are in restricted ranges (i.e., are coming from an unexpected country).  
The important point to make about all these rules is that they only apply to people who are not already on your white list. DigiPortal Software take the position that legitimate people whom you don't know but who are contacting you for the first time would NOT include the items described above, therefore making it safe to delete such messages received from unknown senders.