Hi,   
      
   On 2014-04-23 10:06:52, mark lewis wrote to wilfred van velzen:   
     about: "FMail duplicate detection":   
      
    ml> what does FMail use for its duplicate detection, please?   
      
    ml> on this system, i see numerous false positive duplicates that have passed   
    ml> through the fastecho system of my uplink... i'm trying to track down why   
    ml> FMail would think they are duplicates when FE has not... the FE system is   
    ml> using its largest dupe database option...   
      
   First, I have never noticed a false positive. There were false negatives, when   
   the messages were too old to be in the dupe base.   
      
   Regarding dupe detection by fmail, there are "clues" in the doc file:   
      
   FMAIL.DUP      Contains  the database  with signatures  of messages   
                  used by  FMail to  detect duplicate messages.  FMail   
                  keeps track of the last 16384 messages.   
      
   FMAIL32.DUP    The 32-bit version of the duplicate detection  file.   
                  It is  capable of  keeping track of  more duplicates   
                  than the 16-bit DOS version. (max. 9999*1024).   
      
   Ignore MSGID   
      
             Normally FMail uses the MSGID of a message (if present)   
             for duplicate detection purposes. In some cases, this   
             may cause problems when different messages are having   
             the same MSGID: one or more of these messages will be   
             marked as duplicates although they are not. If you are   
             frequently experiencing these problems, try setting this   
             switch to 'Yes'.   
      
   Dups recs (x1024) (32-bit mode only, start FSetupX with "/32")   
      
             Number of signatures of messages that are stored on   
             disk.   
      
   So it depends on the version you are using and your settings.   
   In the .DUP file a crc32 of some parts of the message (depending on your   
   settings) is stored. If you want to know more about the techincal details of   
   that, look in the source:   
      
   http://sourceforge.net/p/fmail/code/ci/master/tree/DUPS32.C   
   or   
   http://sourceforge.net/p/fmail/code/ci/master/tree/DUPS.C   
      
   In the checkDup function...   
      
      
   Bye, Wilfred.   
      
      
   --- FMail-W32-1.68.1.61-B20140411   
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