http://issues.apache.org/SpamAssassin/show_bug.cgi?id=5790





------- Additional Comments From [EMAIL PROTECTED]  2008-01-17 11:07 -------
> On a failing test a large proportion of NXDomain responses from a name server
> never make it back to the querying host. Is there any misguided firewall
> or router sitting between both hosts which might misinterpret a barrage of
> NXDomain responses as some kind of a DoS attack and drop packets? Or an
> equivalent DoS protection functionality on the host itself?

Perhaps I am not familiar enough with tcpdump, but when I look at the tcpdump
output it looks to me that there are exactly the same number of responses as
there are queries.  So I don't quite understand how one can conclude that
there are large proportion of NXDomain responses from a name server that
never make it back to the querying host.  Note that tcpdump was running on
the machine running the dnsbl test (the querying host).  In any case, there
is nothing between the two machines.  All  the machines that I have been
testing on are connected to the same ethernet switch.  Also, there is no
special softwere running on the failing test machine.  Perhaps Solaris 8
has something like that built in.  In any case, looking at the logs it looks
to me as if the responses are reaching the test machine but are not being
received by SpamAssassin.  Perhaps Solaris 8 can not handle a large number
of responses in a short period of time.  I am wondering why there are so many
queries.  I had thought that the dnsbl test would only query the spamassassin
server.



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