Sender ID, as it is known, is a merged version of Wong’s already-successful Sender Policy Framework and Microsoft’s earlier-stage Caller ID For Email spec. The decision to merge the two specs was reached a month ago.
By providing a unified specification, Microsoft and Wong hope to simplify industry adoption of effective e-mail authentication technology, thereby helping to more swiftly provide greater spam protection to e-mail users worldwide, Microsoft said in a statement.
Sender ID promises to help organizations reduce, but likely not eliminate, spam and email worms, most of which spoof their From: addresses in the headers to evade detection, by asking adopters to publish the IP addresses of their mail transfer agents in the domain name system.
Organizations adopting the spec publish these IP addresses in the publicly accessible DNS, so that receiving MTA servers can look them up and verify that the source address matches those authorized to send mail from any given domains.
This shows that the address has not been spoofed, a factor that can then be used in any filtering decisions that the MTA or spam or virus filters make.
There are already about 20,000 domains that publish SPF records, according to Wong. America Online Inc is the highest-profile company to endorse Wong’s work, and is also backing the merged Sender ID proposals.
Sender ID will provide backwards compatibility with already-published SPF records, Microsoft said. SPF called for text-based records, while Microsoft pushed for XML-based records. Sender ID will support both, Microsoft said.
The spec will also allow the verification part of the process to happen at both the SMTP transport level, as proposed by SPF, and at the message header level, as proposed by Caller ID, Microsoft said. The SMTP-level checking allows messages to be blocked before they are sent, the firm said.
Sender ID, and a related proposal from Yahoo! Inc, DomainKeys, were recently endorsed by other ISPs including AOL, BT and Comcast. Email administrators interested in trying out the proposed spec can download details from microsoft.com/senderid or Wong’s site at spf.pobox.com.
