The List-Unsubscribe header

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 customers, as well as the contacts of 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.

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  • Joly MacFie


    Occasionally a spam gets through on a discussion list to my gmail – I’ve always happily hit the spam button thibking “ah this will help Google heuristics sort out spam from genuine list emails and that they would intelligently understand that if this was from a list I obviously wasn’t suggesting every mail from that list was spam – now I from this I am learning that I may very well have been auto-unsubscribing. Gmail should at least explain it and make it opt-in IMHO.

  • Franck Martin

    No, gmail does not list unsubscribe unless you say so. First for gmail to provide the unsubscribe feature it must believe the unsubscribe will be honored, second if you click on spam and gmail believes the sender honor the unsubscribe, it will offer you to still report the email as spam to google and unsubscribe or just report it as spam.
    On hotmail, when you click spam, it will send a message to the FBL registered sender to say the user has clicked on spam for this email, so stop further spam and will send an unsubscribe. To be (feedback loop) FBL registered, you must be believed to deal with spam reports appropriately.

  • Brooke Ingwerson

    I should say that that the data community appears to be exactly like a house of mirrors in conditions of getting hold of real truth. There may be a lot so called honest data flying all over around but from our practical knowledge it appears like it is just about all the identical rubbish. I happen to be needing for opt-in data files that I’m able to making use of for electronic mail marketing in a few targeted web based segments but what we’ve experienced until now resemble it was plainly harvested off of web sites. Many of the web logs in existence are beneficial but I come to feel dizzy just attempting to sort through all the tales of quality data.