e-commerce deliverability white paper

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E-commerce Deliverability White paper


  • Identifying and managing domain-specific deliverability

    June 2006

    An Experian CheetahMail white paper

  • 2008 Experian CheetahMail, Inc. All rights reserved.

    By navigating the rules of each web domain, marketers can ensure that their email successfully reaches the inboxes of their subscribers


    OverviewUnfortunately, the English language does not have a plural use of the term deliverability. It would be helpful if we did, since the topic of managing deliverability is not a singular use term, but rather one that applies to hundreds of specific domains who each receive email via different filtering methodologies. This whitepaper describes and advises emailers with some of the specific filtering attributes implemented by the largest email receivers in the world and how to help ensure delivery to those receivers.

    In recent years, we have witnessed a renaissance of communications and developments between legitimate email senders and email receivers, of which CheetahMail has been a leading participant. One of the most recognizable outcomes of these discussions is the availability of the junk mail/abuse feedback loop (FBL), which is a direct data feed from the receiver to the sender of recipients who have pressed the junk or spam button. While each receivers implementation of the FBL is slightly different (and there is a pending Internet standard to homogenise these approaches), the bottom line is that senders who receive this data are now in a position to finely tune their email delivery campaigns to ensure that messaging does not exceed acceptable abuse thresholds with these receivers. As we progress through this paper, CheetahMail will list some of the benchmarks and acceptable use metrics senders can use to help manage this new data resource.

    Two other recent developments in the war against spam are the use of Bayesian filters and the use of third party accreditation services. A Bayesian filter is a machine-learning technique that continuously imports message types and content into a filter and refines rules based on observable behavior of email users such as abuse complaint feedback. Receivers such as MSN/Hotmail have spent tremendous amounts of time and effort building Bayesian filters and are continuously adding filtering rule emphasis to it versus other types of filtering mechanisms. Finally, we have recently communicated on some receivers use of third party accreditation services such as AOLs relationship with Goodmail Systems Certified Email programme and Microsofts relationship with Return Paths SenderScoreCertified programme and will highlight their respective receiver implementations in this paper as well.

    FYI: Types of filtersFor the purposes of this white paper, there are three key types of filters which guide us through the ISP deliverability landscape:

    Gateway FiltersThese filters determine message acceptance before they are routed through the actual receiver processing servers. In the positive sense, this is where a whitelist may be enacted to ensure the first level of routing success or where a blacklist may bounce messaging back to a sender before the receiver actually processes the mail.

    Server FiltersOnce past the Gateway, a receiving server will use many different layers and types of email filters to determine how to process the email. In this category are the Bayesian filters described earlier as well as reputation filters such as spamtrap and complaint-rate monitoring. Finally, this category of filter also monitors messaging content such as spam-related keywords and problematic uses of images.

    User-Level FiltersThis last category is the filter where not even the most advanced sender, receiver postmaster, or third party accreditation service can modify these settings. In most cases, these filters can be positive in the case of addressbook entries, but in some cases can be negative in cases where a user blocks senders. For our purposes, we will also note image deployment scenarios in this category.

  • 2008 Experian CheetahMail, Inc. All rights reserved.

    In the past two years, MSN/Hotmails postmaster group has significantly progressed in their efforts to increase transparency and cooperation with the sending community. Some of the highlights of their recent efforts include:

    Sender access to a Smart Network Data Services (SNDS) web portal which is a valuable resource for senders (who control their IP administration) to track and monitor the mail they send to MSN/Hotmail. Included in this portal are daily updated statistics per IP address on the number of spamtraps sent-to, estimated complaint rates, and SmartScreen filter status.

    Implementation of the Junk Mail Reporting Partner Programme (JMRPP), an abuse feedback loop from MSN/Hotmail users who click the Junk button (or Report & Delete button in Windows Live) and directly send this data to senders who agree to suppress those addresses and mitigate future complaints. A partnership with Return Path to offer the SenderScoreCertified third party whitelist, enabling senders who pass accreditation to bypass all MSN/Hotmail gateway/server filters.

    A Snapshot of MSN/Hotmail Filtering Techniques:Gateway FiltersMSN/Hotmail has a long standing relationship with Symantec Brightmail, a third party enterprise filtering provider used by many ISPs. Brightmail utilises spamtraps (often times recycled from previous MSN/Hotmail inactive accounts) and decoy addresses (never used addresses) to identify senders whose mailing practices are suspect. When identified, Brightmail has two distinct filters ISP clients can utilise:

    An IP-based filter identifying the sending IP address and filtering all mail from that address, or;

    A content-based filter identifying keywords, including domain names, of senders or advertisers.

    Often times, when there is a gateway-level block at MSN/Hotmail, senders are required to contact Brightmail directly for resolution and they have the authority to lift a block on behalf of Microsoft.

    [One important note is that in some cases, a Brightmail-related block does not

    Unfortunately, Windows

    Live Mail has also made

    it easier to report junk

    mail when clicking the

    Report & Delete button.

    Adding this button to the

    message-specific interface

    and including the word

    delete are some reasons

    why the percentage of

    MSN/Hotmail abuse data

    exceeds that of other ISP



  • 2008 Experian CheetahMail, Inc. All rights reserved.

    trigger a bounce error message, but rather deletes the message prior to it reaching the recipient. In these cases, senders are required to closely monitor domain performance reports to account for any discrepancies in performance activity.

    Server FiltersAs the largest software company in the world, its not surprising the Microsoft has developed a Bayesian software-based filter that is in use across its servers. The software is called SmartScreen, and learns from more than 500,000 Hotmail users on how they should be identifying spam or junk mail based on complaints and other behaviors. As noted earlier, the SmartScreen filter status of an IP address is presented in the SNDS interface.

    One recent update to SmartScreen is that when a message fails their Sender-ID authentication check, it receives a visible warning in the user interface as well as a negative filter result which could lead to Junk folder delivery.

    User FiltersThe introduction of Windows Live Mail has made things better and worse for email senders with respect to user filters. The bad news is that messages do not show images by default. The good news is that there are two options for users to enable images by default for senders:

    The Allow sender button adds the sender to an Allowed Senders list.

    The Add contact button adds the sender to the users address book.

    Unfortunately, Windows Live Mail has also made it easier to report junk mail when clicking the Report & Delete button. Adding this button to the message-specific interface and including the word delete are some reasons why the percentage of MSN/Hotmail abuse data exceeds that of other ISP FBLs. Another concerning note is that the Report & Delete button also adds a sender to the users Blocked Senders list.

    MSN/Hotmail Complaint Rate Benchmarking: As a participant in the JMRPP, every CheetahMail client now receives direct Junk mail feedback data from MSN/Hotmail. From a volume perspective, this feedback data exceeds comparative volumes of feedback from messages sent to AOL by an average margin of three times (3x).

    To ensure deliverability, CheetahMail recommends these percentage benchmarks for MSN/Hotmail complaint feedback maintenance as a percentage of net delivered messages:

    Normal: Less than 1% Concerning: Between 1% - 2% Moderate risk: Between 2%-3% High risk, investigation warranted: More than 3%

    Sender Management Techniques for MSN/Hotmail:

    Avoid mailing to addresses older than six months that may not have been bounce removed as they could be recycled as spamtraps.

    If a mailing from a private IP network goes into bulk, request that days SNDS SmartScreen filter status from your account manager or by emailing privacy@cheetahmail.com.

    Regularly download and

    separate your abuse

    complaints by domain and

    continuosly monitor

    complaint rates by

    acquisition source,

    frequency of mailings, and

    behavioral history and

    modify messaging

    according to trends.

  • 2008 Experian CheetahMail, Inc. All rights reserved.

    2008 Experian CheetahMail, Inc. All rights reserved.

    Avoid uses of large file images or entire body