An E-Mail Marketer’s Guide to Deliverability, Part 2: Sender ID

Part one of this series looks at the new technologies that help with email deliverability, SPF (define) in particular. Another emerging technology is Sender ID. As with SPF, Rick Buck, director of e-media and privacy/ISP relations at e-Dialog, helped me understand Sender ID and how it differs from SPF.

Here’s the scoop, in plain English.

Sender ID

Sender ID takes email authentication a step further than SPF. As with SPF, Sender ID technology confirms the server is authorized to send email on behalf of the domain names listed. Instead of verifying the “envelope address” as SPF does, Sender ID looks at the purported responsible address (PRA) or “message from” address, which is a little deeper inside the email message.

Like SPF, Sender ID confirms the address at the domain-name level. This means it can confirm an email came from a Yahoo server, but not from a specific Yahoo user. One selling point for Sender ID is it can handle forwarded email for which multiple sender addresses are involved better than SPF. Many technology folks agree Sender ID provides more reliable “proof” of an email message’s origin.

Now, the rub: although SPF is a bit controversial, Sender ID has ignited a firestorm. I won’t go into all the tawdry details, but it’s almost as good as an episode of “Desperate Housewives.”

Sender ID got a lift in August 2004 when the Email Service Providers Coalition (ESPC) reiterated its support for Sender ID while acknowledging it’s only a first step toward solving the spam problem.

Then, in September 2004, the MTA Authorization Records in DNS (MARID) working group, which was tasked with defining a universal email authentication system, was shut down. The reason given by its parent, the Internet Engineering Task Force (IETF), was lack of agreement on basic issues, many involving Sender ID.

Sender ID was a lightning rod for discussion at a November 2004 summit on authentication sponsored by the FTC. Why? Sender ID was developed by Microsoft, which is in the process of patenting key parts of the technology. Licensing requirements that often surround patent technologies are what concern open source advocates. They say these requirements typically preclude use in open source software, which is the foundation of the Internet world.

Just last week, MX Logic reported 13 percent of the spam it filtered in January was found to be Sender ID or SPF compliant, suggesting neither technology is really a viable solution to the spam problem. It also questions whether additional resources dedicated to either are worthwhile.

But don’t count Sender ID out quite yet. It’s been rumored to be dead before, notably last year, when partner AOL announced it would no longer support it. AOL came back to the table when Microsoft made the technology SPF compatible.

All the major email service providers (ESPs) have announced their outbound email complies with Sender ID and SPF. Senders who have updated their DNS (define) entries to include their SPF records won’t necessarily need to publish a new record for Sender ID, though Microsoft recommends ESPs may want to.

Microsoft has begun to implement Sender ID checks on email coming into MSN and Hotmail accounts. It’s only one factor in a scoring system to determine what email is spam. Microsoft says it will increase the weight Sender ID carries within that formula as the company sees how it works going forward.

Where will the email world net out on Sender ID? Wish I knew. Meanwhile, it’s an intriguing debate to follow. Here are some resources to learn more:

  • The Apache Software Foundation explains its opposition to Sender ID in a position paper.
  • Microsoft’s Sender ID Home Page has a brief overview of the technology and lots of technical information to help you implement it as a filer or make email you send compliant.
  • Wikipedia’s Sender ID area is light on content but heavy on links to resources representing both sides of the issue.

Next, we’ll cover DomainKeys, which many see as an improvement on both SPF and Sender ID, if still not a perfect spam solution.

Want more email marketing information? ClickZ E-Mail Reference is an archive of all our email columns, organized by topic.

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