On the <ietf(_at_)ietf(_dot_)org> mailing list there has been discussion of
Principles of Spam Abatement. This is a brief summary of principles
which _may_ have consensus of that list. I accept full responsibility
for editing errors and misunderstandings.
- All communications must be by mutual consent.
- The spam problem starts with freely accepting mail from strangers.
- Spam is and will remain a long-term battleground and it needs serious
effort to counter.
- Every mail message carries a practically unforgeable token: the IP
address of the SMTP client.
- It is pointless to erect some expensive Maginot Line and pretend it
will solve the problem.
- There is not and can never be a hoop low enough to pass all human
strangers but exclude spammers' computers.
- If you want more of something, subsidize it; if you want less, tax it.
- Spammers need scale because they get a very low return. Therefore,
part of the solution should be to deny scalability to spammers.
- If we can communicate to the sender (without adverse side effects)
that a message is discarded, then occasional false positives aren't
as much of a problem.
- If you reject the message during the SMTP session you don't need to
generate a bounce message, the other side will do this.
- Errors returned after the close of the SMTP transaction are likely
to go to an innocent party; and should be deprecated for any email
identified as spam.
I also recommend perusing the summary of principles expressed on the
Next-Generation Mail <mail-ng(_at_)imc(_dot_)org> list at:
John Leslie <john(_at_)jlc(_dot_)net>