On 01/23/2014 03:42 PM, Jim Shupert wrote:
The second cause might be excessive clamav scanning times. If clamav
takes too long to scan, the sending client (be it an external server
or a submission client) can time out the connection thinking the
message hasn't been sent, and retry. Upon eventual successful
completion of scanning, QMT will deliver the message, but fail to
notify the sender of such because the sender timed out. After a period
of time, the sender will re-try sending, resulting in a duplicate. The
most common cause of this I've seen is with Outlook. Outlook clients
should be configured for maximum time to time out, which generally
fixes the problem (without really impacting Outlook performance).
Question : when you say " excessive clamav scanning times " would this
always be the scanning of that email
or is it possible for clamav to be bogged down with someone elses email.
meaning
email 'a' is sent , email 'a' has excessive clamav scanning time so
email 'a' is sent again .
or
email 'a' is sent but clamav is bogged down scanning a big
email/attchment of email 'z' currently making email 'a' ---wait.
timeout is exceeded and email a is sent again.
thanks
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Primarily the former.
In the second scenario, email 'a' wouldn't wait (they're not single
threaded ttbomk), but if performance is bad enough (think load of, I'm
guessing, 8 or higher) emails such as 'a' (and others) could time out.
The problem tends to exacerbate itself.
I should mention that this was most common when a certain clamav version
with a bug would eat 100% of a single cpu. I haven't heard of that for
over a couple years now, but long scan times always provide an
opportunity for duplicates to occur, due to a sender (or submitter)
timing out before QMT has finished the scan and had a chance to reply.
Bottom line, Outlook clients should be configured to use the maximum
timeout value (there's a slider control for that - I don't recall off
hand the max value). That doesn't affect user experience at all, because
Outlook has its own queue.
--
-Eric 'shubes'
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