You may have seen on Mailman, Sympa or Lyris the use of the List-Unsubscribe header in emails. This header is not really part of the RFC standards but it is widely recognized to provide a hint on what to do to unsubscribe from mailing lists (RFC2369 is still a proposed standard). Until recently no email client was using this header, and it was left to the reader to check his/her email headers and make use of this information, something that very few users know how to do.
Then came this announcement from Google in July 2009 that they will use this header to send back an unsubscribe email if the user reported email as spam. They would also provide a possibility for users to unsubscribe without reporting the email as spam. Google stated that they would offer this capability to senders under two conditions. First the header must provide an email address and it may optionally contain a web link. Second, the sender must have a sufficiently good reputation and be known to process unsubscribe requests. Google did not want to send back unwanted emails, or worst have people misuse this feature to create spam emails generated by Google.
This mechanism is a good alternative to a bulk email feedback loop, which Google Mail doesn’t provide. It offers advantages for Genius.com customers, as well as the contacts of Genius.com customers—we want our customers to nurture their contacts by building good relationships. Supporting this feature will also be beneficial with other webmail providers as they add support for the list-unsubscribe header.
Like most senders, we use a Variable Envelope Return Path (VERP) to be able to recognize bounces from our emails easily. From there, it is easy to have our MTA, MessageSystems, add an extra header in the email:
if envelope :contains "from" "b03-" {
$from_envelope = envelope "from";
ec_header_add "List-Unsubscribe" "<mailto:u${from_envelope}?subject=unsubscribe>";
}
We prepend the VERP address with “u” to differentiate it from bounces. What is left is then to have a mailbox to receive these emails and a processor to read this special mailbox and optout the contact from the correct sender list.
Our emails look like this, you see the VERP being included:
From Gmail, you need to click “show details” to display more information about the email, notably the unsubscribe link:
When a contact clicks the “Unsubscribe from this sender” link, Gmail sends a message to Genius:
It is then easy to pick up the To: field and process the optout request. Genius always includes an unsubscribe footer in all the emails we send. Sometimes we duplicate it as a header to make it easier for the recipients, but many have learned not to trust these links. Providing another means to unsubscribe/optout where the email provider does the reputation analysis for the user is very valuable.
We have already noticed other unsubscribe emails coming from Hotmail, Comcast and Lashback users. In the case of Hotmail, it seems we receive an unsubscribe for every feedback loop email we receive. At the moment, no email client provides this feature as it would require to evaluate if the unsubscribe request is likely to be honored. Senderscore sometimes contains this assessment when evaluating a sender. With DKIM signing, this analysis could be made much simpler. We do include the List-unsubscribe header in our DKIM signature to prove it is a full part of the email.
While it is not indicated anywhere, it seems the consensus is to not send an email confirming the unsubscription. Email marketing software usually directs the unsubscriber to a page to indicate a procedure should they wants to re-subscribe later. A List-Unsubscribe header means the user has requested not to receive any more emails. A confirmation email would be seen as just another email.
