Re: An Anti-Spam Heuristic

On Dec 13, 2012, at 12:59 PM, Seth <[email protected]> wrote:

> Barry Shein <[email protected]> wrote:
> 
>> There's also Jef Poskanzer's greymilter which basically requires one
>> re-send from each never before seen mail server not in a white list.
>> 
>> And sendmail (and others') HELO delay (delay sending HELO a short
>> period of time) and don't speak until you're spoken to whatever they
>> call it (I use it, the sender must wait for the SMTP responses, can't
>> just dump an SMTP conversation at you.)
>> 
>> They're basically isomorphic to hashcash type solutions, increase the
>> sender's cost, but very transparent and quite clever because of that.
> 
> They have nothing to do with increasing the sender's cost.  Rather,
> they take advantage of the fact that legitimate mailers implement the
> RFCs in ways that spamware typically doesn't, so they test for that
> and spamware flunks.

And a lot of spamware doesn't flunk. Yet it can damage legitimate use of email,
both when the senders aren't following RFCs strictly (lots of senders will
give up if a recipients MX is so overloaded/broken that it's not responding
after tens of seconds) or when they are (greylisting in particular really
breaks active mailing lists, by reordering discussions into a fairly random
order).

It's the sort of thing that people tend to do because it makes them feel
like they're sticking one to spammers - which isn't a bad reason, by any
means, but doesn't lead towards optimal solutions.

Cheers,
  Steve