[Cryptography] email from strangers -->

[John Denker]

On 09/10/2014 07:57 AM, John Levine wrote:

> One of the reason that SMTP mail wiped out all of its competitors is
> that it allows unintroduced mail.  It doesn't have to be extremely
> easy, but it does have to be possible.

Agreed!  For details see below.

>  I don't get a lot of non-spam mail from people with whom I've
> never corresponded, but the trickle I get is often of high value, from
> "are you the John Levine I knew in college?" to "are you available for
> this highly lucrative contract?"

+1 to that.

I get a lot of email from unintroduced strangers.  In particular,
I solicit comments about my web site, and 99% of the comments
have value.  Even the ones that might seem like dumb questions
I take seriously, because they indicate that my writing is not
as clear as it should be.  Far less than 1% of the comments 
come from out-and-out cranks.

If I didn't have a spam filter I would be deluged with spam,
but in fact verrry little spam makes it past the filter.

====================

If spam ever did overwhelm filter technology of the existing
kind, there is other technology that could be applied.

For one thing, I could insist that all unsolicited email
bear a payment of 49 cents (equivalent to US first-class
postage) payable to me via some cryptologically-secure 
e-payment scheme.  

I promise not to collect the payment unless I actually
read the message.  I furthermore promise not to collect
the payment if I consider the message to be interesting
or otherwise non-obnoxious.  Anybody who thinks my time 
is not worth 49 cents should please not send me email.
There is some risk that I could collect the payment
without reading the email, but that just means that
when we remove risk from the recipient (the unbounded
risk of spam) we are shifting some risk onto the sender 
(the bounded risk of poor return on the investment of
postage).

A check for 49 cents would be more than sufficient to 
stop spammers cold.

  Note that electronic /currency/ is not the right
  model here, because if you send a stranger some
  currency, you don't know whether it got lost or
  is just being hoarded.  You need a /check/ model
  with an expiration date, such that if the recipient
  does not cash the check by a certain date you get
  your money back.

  In some vague sense, PayPal is close to the right 
  model, if we ignore details such as being insecure
  as well as generally obnoxious.