Greylisting (WAS: gif attachments)

[DAve]

Daniel Maher wrote:
> 
>> -----Original Message-----
>> From: mailscanner-bounces at lists.mailscanner.info [mailto:mailscanner-
>> bounces at lists.mailscanner.info] On Behalf Of Julian Field
>> Sent: August 23, 2006 4:29 PM
>> To: MailScanner discussion
>> Subject: Re: gif attachments
>>
>>
>> Try implementing greylisting on your servers. This has helped a lot with
>> this problem on my systems.
>> Even if you set the greylisting delay as low as 5 minutes.
> 
> My big fear w/ Greylisting is that a (legitmate) SMTP server somewhere won't respect the "try again later" code, and instead just fail to deliver the mail.  I've heard rumours that some of the larger webmail providers exhibit this behaviour.
> 
> Comments?

We just configured greylisting on all our gateway servers this week. Our 
spam percentage (caught) dropped dramatically, because the number of 
messages which made it into our servers fell by over 70%. Very nice, our 
servers are bored now. We should have had over 80k messages today yet we 
are showing only 30k have made it inside so far. Now that five oclock is 
here, the percentage of good messages will fall fast.

For what it is worth we went with Milter-greylist 2.02 as it provides a 
sync ability between multiple MXs. Note also that the conf file already 
has a large list of mail servers that do not honor temp failures and 
they are whitelisted from the gitgo. You can also whitelist IPs, rcpt 
addresses, sender addresses, regex addresses, domains.

So far we are very happy.

DAve


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