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