>
>Recently I've been getting two copies of space digest one right after
>the other.  The copies are identical, but I don't always get two of
>each.  A TRACK snapshot of the listserv console output is included
>below.  Is this the proper place to report possible duplicate mailing?
>The  Space Digest issue in question is Vol 9 issue 74.
 
   If the digest originates on the Internet, there is a possibility of
duplication by SMTP.  RFC 1047 by Craig Partridge, "Duplicate Messages
and SMTP" (2/88) describes the problem.  (You can get the RFC in LISTING
format from LISTSERV@TCSVM as RFC1047 LISTING in the RFC filelist).
 
   The problem occurs more between some pairs of sites than others.
Basically the problem is that one system accepts the mail but does not
confirm it with the other system before the connection is severed.  So
the sending system will resend the mail later.  Several factors and
remedies are discussed.  For example, I think the RFC has influenced
some of the design changes in IBM's SMTP server (current and/or future...).
 
   The most useful thing I have found to track down the problem is simply
sending the LISTSERV distributing the list to me the  SET listname FULLHDR
command.  You can easily compare the "Received:" lines for the point at
which the times differ.  It is that connection which is creating the
duplicate.  In the past the duplicates, when they occured, came on the
same connection each time.  Of course they didn't always appear and it
would be possible to get more than two copies.
 
   Your results may differ.  Different in California...   :-)
 
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Marty Hoag
ND Higher Education Computer Network    US Mail: NDSU Computer Center
Phone: (701)-237-8639                            PO Box 5164 / UCCS
Bitnet:   NU021172@NDSUVM1    (NOTE 0 = ZERO)    Fargo, ND  58105
Internet: [log in to unmask]
UUCP:    ...!psuvax1!NDSUVM1.BITNET!NU021172