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Re: [LI] Duplicates - cool it!



Hi,

Atul Chitnis typed:

> We know that there is a problem, and we are trying to fix it.

The problem of duplicate mails could be the one described in RFC 1047.

Quote:

   The synchronization problem occurs at the end of delivering a
   message.  When the sending mailer has finished sending the text of a
   message, it is required to send a line containing a single dot or
   period.  When the receiving mailer receives this final dot, it is
   expected to do its final message processing and either confirm
   receipt of the message (with a 250 reply) or reject the message with
   any one of several error codes.

   Observe that there is a potential synchronization gap here.  During
   the period between the time the receiving mailer has determined that
   it will accept the message, and the time that sending mailer gets the
   250 reply, the message is active at both the sending and receiving
   mailer.  Until the sending mailer gets the 250 reply, it must assume
   the message was not delivered.  After the receiving mailer has
   decided to accept the message, it must assume the message has been
   delivered to it.  If the communications link fails during this
   synchronization gap, then the message has been duplicated.  Both
   mailers have active copies of the message that they will try to
   deliver.

   Many mailers delay responding to the final dot because they are doing
   sophisticated processing of the message, in an attempt to confirm
   that they can deliver the message.  For example, the mailers may
   expand an entire mailing list to confirm that it can reach all
   addressees or may attempt to physically deposit the message into the
   mailboxes of local users, before confirming receipt of the final dot.
   These practices are not unreasonable, but they often cause the
   synchronization gap to continue for several minutes, and increase the
   likelihood that the sending mailer will timeout or the network will
   fail before the accepting 250 reply is sent.

   The best way to avoid the synchronization problem is to minimize the
   length of the synchronization gap.  In other words, receiving mailers
   should acknowledge the final dot as soon as possible and do more
   complex processing of the message later.

   Some mailers can be configured to do more or less processing upon
   receipt of the final dot.  In such situations, the mailer should
   always be configured to do less processing.

Unquote

For more details, check RFC 1047.

Thaths, maybe you could look into this..

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