> The exact source of the problem was a limit in threads in MS SMTP,
> which is something like 20 per processor (not sure if hyperthreading
> counts in this case). . .
This isn't an accurate claim. It sounds like you just haven't tried to
tune MS SMTP appropriately for load/resources/growth. That's fine,
since MS doesn't push you too hard on this, but please do some more
lab work before deciding that MS SMTP is broken.
Look into the following values:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\InetInfo\Parameters\PoolThreadLimit
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SMTPSVC\Queuing\MaxPercentPoolThreads
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\SMTPSVC\Queuing\AdditionalPoolThreadsPerProc
You also need to realize the differences between I/O completion port
architecture, callbacks, and pure multithreading. It's possible to
bottleneck anything, but that's an implementation problem with a given
event sink, not a problem with the overall framework.
> . . . this limitation in the MS SMTP architecture makes it
> inappropriate for any full scale spam blocking solution such as
> Declude unless you have that application ride behind MS SMTP instead
> of being plugged into it. . . .
Sorry, man, but that's FUD. I appreciate what you found with FTP in
your config, but let's not jump over the available data.
> One other note. I had previously used the Windows registry hack to
> enable a native tarpitting feature in MS SMTP with even worse
> affects. The built-in tarpitting in MS SMTP will delay all 5xx error
> codes by the time that you set, and this included the 552 error used
> when messages are over the maximum size. The result of this terrible
> oversight is that a fair number of servers will not recognize the
> delayed 552 error and will requeue the oversized messages over and
> over again, and that eats up a lot of bandwidth real, real quick.
Matt, you _know_ this isn't cause and effect, since you and I both
looked at a specific server _without_ tarpitting enabled that
exhibited the problem with oversize messages. There may be an
additional wrinkle added by ttarpitting, but it's not the root cause
of the problem.
--Sandy
Sanford Whiteman, Chief Technologist
Broadleaf Systems, a division of
Cypress Integrated Systems, Inc.
e-mail: [EMAIL PROTECTED]
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