RE: uncatchable spam

The time is actually unimportant as the spammers for the most part don't resend at all.  Most mail servers will attempt to resend within 15 minutes after a soft failure.

Different greylists operate differently.  What mine does is tracks the "From"/"To"/"server" triplet, and places a 15 minute TTL timer on the provisional triplet database entry.  
If the message is resent before the provisional TTL expires then the triplet is approved and moved to the approved database with a 72 hour TTL.  Subsequent messages with the same triplet are delivered and the approved TTL timer is reset.

Most greylists have some provision to aggregate multiple MX's or smtp servers per domain to accommodate places like hotmail that have a lot of outgoing mail servers that email may round-robin from.  

The greylist should also have provision to whitelist non-RFC compliant servers that you decide to accept email from.

If you see performance issues because of greylisting then you can consider exempting servers with valid SPF from greylisting.  



 

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> On Behalf Of Jim Pazarena
> Sent: Tuesday, October 05, 2010 11:48 AM
> To: [email protected]
> Subject: Re: uncatchable spam
> 
> On 10/5/2010 9:44 AM, Kevin Kargel wrote:
> > I am sysadmin for an ISP..  I agree that filtering for customers based
> on To/Cc would not be appropriate unless directed by the customer.
> >
> > Greylisting, however, makes a huge difference.  This morning, for
> example, out of 130K emails presented to my mail server 110K emails did
> not pass greylisting.  I did not receive any complaints of missing email.
> 
> very good advice.
> Thank you.
> 
> Greylisting 'delays' reception. What time limit do _you_ find is the least
>   intrusive / most effective?
> --
> Eat sushi frequently. - Avi
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-- 
Eat sushi frequently. - Avi
[email protected] is the human contact address.
[email protected] is the list posting address.
See below URL for subscribe/unsubscribe and list options:
http://inet-access.net/mailman/listinfo/list