OT - Greylisting (was: Re: gOCR SpamAssassin plugin)

Julian Field mailscanner at ecs.soton.ac.uk
Sat Aug 12 15:28:51 IST 2006

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mikea wrote:
> On Fri, Aug 11, 2006 at 01:05:18PM -0400, Michael Baird wrote:
>> On Fri, 2006-08-11 at 10:52 -0500, Logan Shaw wrote:
>>> On Fri, 11 Aug 2006, Jim Holland wrote:
>>>> Another concern is the impact that greylisting would have on the Internet
>>>> if its adoption became widespread - it would mean that all mail servers
>>>> would have to work twice as hard to deliver mail.
>>> Actually, it's only some mail servers.  Greylisting lets known
>>> senders through without a delay.  Mail servers that are mostly
>>> sending messages to recipients who recognize them would not
>>> see delays.  Mail servers that are mostly sending messages
>>> to those who don't recognize them would see the delays.  So,
>>> it makes mail servers up to twice as hard.
>>> Also, while I agree that it would increase the load, in
>>> general I think decreasing spam is worth some increased load.
>>> Sure, it's a slippery slope (one could imagine things getting
>>> so bloated that it takes 5 minutes of CPU time to deliver one
>>> message, if we keep on adding limitless spam-fighting strategy),
>>> but on the other hand, 10 seconds of CPU time spent catching
>>> spam automatically is cheaper than 10 seconds of a human's
>>> time deleting it manually.
>> Greylisting decreases load immeasurably on a mailscanner system, the
>> cost of greylisting is much less then allowing the message to go through
>> the mailscanner sytem. I deployed it several months ago, it really is a
>> good tool, and I've had very few complaints (10000 users).
> My complaints have, almost without exception, come from users who think
> that E-mail should show up in their inboxes Right DamnIt _NOW_.

I have 2000 users who are just like that, they use email instead of the 
phone quite a lot of the time. And why not, after all, it's pretty 
instant and they get to re-phrase what they say before the recipient 
gets it. I do it myself.

So I set the delay to 10 minutes, with the memory time set to 32 days. 
32 days means you effectively whitelist all the monthly emails from 
mailing list servers, as I don't want to make list servers' lives any 
harder than they are already.

I talked to some of my fussiest users, and to my top management, and 
persuaded them to take part in an email spam fight test for a week. I 
refused to tell them what I was doing, just that they wouldn't lose any 
real mail and were quite safe.

After the test, I asked them for the experiences, particularly any 
"hunches" or "feelings" they had about what had happened in the past week.

Not *one* person commented about any delay.

I have now deployed it across the entire place, and they love it.

So do a totally blind test with your fussiest users, like I did. And 
then go for it! :-)

- -- 
Julian Field
Buy the MailScanner book at www.MailScanner.info/store

MailScanner customisation, or any advanced system administration help?
Contact me at Jules at MailScanner.biz

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