I find this *really* annoying

[Derek Martin]

On Thu, Apr 07, 2005 at 03:24:18PM -0400, Travis Roy wrote:
> Where did he say that he did not have business class? I had business 
> class DSL and my IP range was still considered within a "dynamic" pool.

Well, I happen to know that he doesn't, but your point is well taken.
Some RBLs are careful to only block mail from IPs which are reasonably
verifiable as spammers, but SORBS method is completely arbitrary.
Just because an address is in a range that is served by DHCP doesn't
necessarily mean that the user is a home user, nor does it necessarily
mean that their ISP disapproves of them sending e-mail from their own
systems.

Some time should probably also be spent on explaining why SORBS is
sometimes used as the sole factor in deciding whether to block e-mail.
The fact is, using SORBS from within the MTA/MDA requires only a very
low commitment of system resources, whereas using most other filtering
techniques require substantially more system resources.  Especially
for very high volume sites, it's more cost effective.  Or at least it
seems that way...  Businesses need to also factor in the cost of lost
business due to legitimate mail which was blocked by SORBS, which is
hard to do...  If I sent mail to a company requesting services to a
business, and their mail server blocked my e-mail, I'd personally be
strongly inclined to turn to a competitor without making any further
inquiries.  I suspect I'm not alone...

Filtering all mail through spamassassin or a similar filter requires
substantial CPU cycles (potentially, depending on how it's
configured), whereas relying solely on SORBS only costs a single DNS
lookup.  I think the cryptographic signature method is a decent
trade-off.  It requires DNS lookups to get the keys, and some CPU
cycles to verify the signature, but it's harder to forge than a single
DNS entry, making it more reliable than other DNS-based methods, and
virtually guarantees no false positives, so long as site admins for
any given domain do their job...

-- 
Derek D. Martin    http://www.pizzashack.org/   GPG Key ID: 0xDFBEAD02
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