I should point out that "typical" greylisting doesn't work well with Gmail, since there is no guarantee that the retries will be performed from the same IP address... in fact, the chances are really high that it's from a different one.
By typical, I mean based on any tuple which includes IP. We will try multiple hosts in preference order if we fail connections to earlier hosts or if the hosts return a 4xx banner. We do also "learn" down hosts, and will skip them without trying for limited periods of time (given the mechanism there, it probably is only really used for fairly high volume domains). I can only imagine how greylisting would actually lead to that, unless it was causing increased load resulting in slow responses or connection failures, or if the box has some sort of attack mode where it would start blocking connections earlier. Brandon On Thu, Feb 25, 2016 at 3:04 PM, Adrian Neale (iComms) <[email protected]> wrote: > Hi there, not sure what the correct protocol for answering these things > is, but here goes so at least you know it has been resolved. > > After looking at the logs myself from the shell of the Sophos UTM, the UTM > was in fact Greylisting. > > Why Sophos did not originally spot this when I raised the call with them I > do not know. Also, why is it only affecting Hotmail/Gmail/Outlok.com, I do > not know. > > Anyway, so the emails are following the right MX records in the right > order. > > They are getting Greylisted and are arriving at the 3rd priority MX record > queuing service (which does not Greylist) and are being delivered back up > to the primary MX record. > > So all behaving as expected, well, kind of, but at least I know why. > > Thank you for all your suggestions, they helped me identify and understand > the problem with a bit of digging on my part. > > Kind Regards, > > Adrian. > _______________________________________________ > mailop mailing list > [email protected] > https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop >
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