Greylisting (WAS: gif attachments)

John Rudd jrudd at
Thu Aug 24 00:15:04 IST 2006

On Aug 23, 2006, at 14:02, Daniel Maher wrote:

>> -----Original Message-----
>> From: mailscanner-bounces at [mailto:mailscanner-
>> bounces at] 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.

You kind of have to make the decision of whether you're going to 
enforce standards and endure the complaints from idiots within your own 
organization (who, unfortunately, might be politically powerful idiots) 
... or you're going to not have hard and meaningful standards in the 
name of practicality.  Not an easy decision in some environments.

The unfortunate part is, it sometimes depends on whether or not your 
boss and bosses boss, etc., will shield you from the fallout of 
enforcing standards.  I personally think that's the better path.  But 
no one outside of your organization can really say whether it'll work 
for you.

My personal answer, though, is: No SMTP server which behaves in the 
manner you describe qualifies for the label "legitimate".  But, my 
definition of legitimate may vary slightly from yours.

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