[Mimedefang] SURBL effectiveness and domain turnaround time

Jeff Rife mimedefang at nabs.net
Wed Sep 8 23:11:27 EDT 2004


On 7 Sep 2004 at 20:15, David F. Skoll wrote:

> Well, there is an absolute lower limit on the useful lifetime of a
> domain.  A spammer probably can't throw a domain away in much less
> than 4-8 hours, because it takes that long to complete the spam run
> and for victims to go check their mail.  Although I check my mail
> practically continuously when I'm at work, many people only check
> their mail a few times a day.  If SURBL can react within 15-30
> minutes, it will still remain quite effective.

This is a good thought, but caching of DNS records defeats this.  I 
know that most BLs have low TTL in the records, but lower than about an 
hour would cause a lot of extra network traffic, especially on the "not 
found" responses.


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