Frequent duplicates

[Jonathan de Boyne Pollard]

BM> Message-ID (these appear to be generated by ISC's mail-to-news gateway)

The ISC's gateway unconditionally replaces existing Message-IDs on 
posted newsgroup articles with its own.  I see all of my articles come 
back from ISC's gateway with ISC-assigned Message-IDs different to what 
they had when they were sent.

Of course, the act of overwriting Message-IDs like this is one of the 
well-known ways of causing such problems as you have observed.  It's the 
classic way of enabling a "dupe loop".  And it's discussed at length, as 
bad practice, in the IETF USEFOR draft.  (See sections 5.3 and 8.8 /et 
seq./.)

It's also one of the well-known problems with other broken softwares.

<URL:http://homepages.tesco.net./~J.deBoynePollard/FGA/lyris-problems.html#NewsLoops>