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DNS Error:TimedOut

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hookjd View Drop Down
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    Posted: 07 May 2009 at 8:33pm
I am seeing over 100 log entries daily that say "DNS Error:TimedOut".  It seems to happen with any of the DNS servers I have spamfilter configured to use.  I don't believe there is anything I can do about it, but it appears to me that spamfilter defaults to sending the email when this occurs.  Is that true?  Is there anything that can be done to make it queue up and try again to query the DNS?  I am trying to figure out why so much spam is getting through my machine lately and I've looked at the whitelists and made a lot of adjustments.  This issue just sticks out to me as something I should address.  What are your thoughts on DNS Query Time Outs?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LogSat Quote  Post ReplyReply Direct Link To This Post Posted: 07 May 2009 at 11:07pm
When there is a DNS timeout, SpamFilter will skip the specific dns query that timed out and will continue with the next query/filter - so the email is not allowed thru right away as usually many more tests will be performed.

Having SpamFilter retry on DNS failures would be a rather potentially big problem. If the DNS server(s) SpamFilter uses are completely down, every single query may time-out. Having retries could mean that an email that would normally take 1 second to process may take 20-60 seconds to process as multiple timeouts need to be waited upon. This would create a potentially ever-growing queue up of incoming emails that could not be processed in time, which could bring the SpamFilter server to its knees.

In regards to the amount of timeouts, it is normal for a small percentage of incoming connections to contain DNS timeouts during the various DNS tests. As a reference, on our own logsat.com mail server yesterday we processed about 30,000 incoming connections, which resulted in about 400 DNS timeouts (one every 3.5 minutes or so).
Roberto Franceschetti

LogSat Software

Spam Filter ISP
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hookjd View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote hookjd Quote  Post ReplyReply Direct Link To This Post Posted: 08 May 2009 at 12:18pm
Very helpful.  thanks as always for the quick response times to questions like this.  It keeps me using this product!
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