Unsolicited email has a high annoyance factor because they
consume attention-time and they junk up the inbox. Some
spam-filtering techniques generates false
positives, so the user ends up having to trawl through
their Junk folder looking for legitimate email. Any scheme
which makes the reader spend time reading the mail rewards
the spam sender.
Assuming we operate with client-side whitelists, what if
non-white-listed email is quarantined (just left on the POP-server)
and the email client sent the user a list of quarantined messages
in a digest form? eg:
Subject: Quarantined email
Email from the following senders have been quarantined.
You can preview the emails on the web by clicking
on these links or you may unquarantine the sender.
Individually mailed messages (* indicates the number of
computational tokens paid to receive your email)
---------------------------------------------------------
***** Sally Morten <smorten(_at_)test(_dot_)com>
* E-bay <e-bay-purchase-308852(_at_)ebay(_dot_)com>
Grey-listed email (email received from sites you have
recently visited)
---------------------------------------------------------
Weekly-newsletter <listserv-asrg(_at_)ietf(_dot_)org>
Bulk mailed messages (sent to multiple recipients, the emails
more likely to be unsolicited advertisements appear at
the end of the list):
---------------------------------------------------------
DeveloperWorks <newsletter-developerworks(_at_)ibm(_dot_)com>
.
.
John Black
<buy-viagra-from-viagraweb(_dot_)com(_at_)viagraweb(_dot_)com>
.
.
.
The idea here is that if you are sending email for the
first time (to an old friend, when apply for a job, or
a list-server notifying the user of mail-subscription) you have
to pay computational tokens to get the attention of the user.
An intelligent email client could even decide that
<listserv-asrg(_at_)ietf(_dot_)org> shoudl be gray listed, since the user's
internet logs could be cross referenced.
The benefit of the scheme proposed are
o does not require any changes to the
SMTP protocol as all the processing is done on the
client-side.
o the implementation could be achieved with a client-side
proxy, leading to fast adoption.
o White-listed could be automated using the client's
address book, achieving rapid training of the system.
o Quarantined email is left on the POP server, conserving
a client's limited dial up bandwidth resources.
There is probably some scope for the extension of POP protocol
to help the client identify spam emails, which may score emails
based on the probability that they are spam.
On an aside: here's something to think about: Spam may include
corporate information. If one operates in a large organisation, bulk
mailed corporate communications junk up the inbox as well.
Client-side tools should make sorting out what is urgent and what
isn't.
Chui Tey