Novel Method for Universal Email Authentication

MKaplan writes "Most spam is sent using spoofed domains. Email authentication schemes such as SPF attempt to foil spoofing by having domain administrators publish a list of their approved outgoing mail servers. SPF is sharply limited by incomplete domain participation and failure to authenticate forwarded email. A paper describes a novel method to rapidly generate a near-perfect global SPF database independent of the participation of domain administrators. A single email from an unauthenticated domain is bounced and then resent — this previously unauthenticated domain and the server listed in the return path of the resent bounce are entered into a globally accessible database. All future emails sent from this domain via this server will be authenticated after checking this new database. Mechanisms to authenticate forwarded email and to nullify subversion of this anti-spam system are also described."

Comments

Fails to account for SMTP farms...

[pathological liar]

So what happens when you receive an email from a big site like Sympatico, Hotmail, or any number of other places that have farms of SMTP servers, where your message isn't guaranteed to be resent from the same IP?

This also requires users to install software to use effectively, and features CAPTCHAs which are a usability nightmare and not nearly as impregnable as the author thinks.

All that effort instead of just adding a TXT record to their domains.

Major flaw in methodology

[Todd Knarr]

The proposed scheme ignores one thing: the majority of bounce messages today are false bounces caused by spammer joe-jobs, therefore they themselves get flagged as spam and deleted/ignored. In addition, it also increases the annoyance of greylist authentication schemes, since a spammer forging my address in the From field will cause every host participating in this scheme to send me a verification e-mail for a message I didn't send which I'll have to deal with. The proposed scheme makes a very fundamental mistake: assuming that you can trust the sender's address in a message to be the true sender's address. You can do that only after you've determined the message is authentic and not spam, at which point you don't need this scheme anymore.