E-mail Bounces, Hard and Soft

  |  May 17, 2007   |  Comments

Sort out the confusion over e-mail bounce terminology and build a more effective list.

Whenever I discuss bounces with marketers, someone inevitably asks about hard and soft bounces. Virtually every information request that crosses my desk asks whether we split bounces this way. A straw poll of deliverability professionals indicates they all struggle with the same issue: disagreeing with the concept of hard and soft but having to live with it.

The reason for this preoccupation is the psychologically neat and intuitively obvious differentiation between temporary and permanent bounces. Unfortunately, the real world is nowhere near as tidy; using these artificial distinctions can be very harmful to your metrics and lists.

There's no agreement on hard and soft bounce definitions. The e-mail delivery protocol, SMTP (define), classifies failures as transient or permanent. Some people consider a soft bounce to be a transient failure and a hard bounce a permanent failure. This is an excellent, accurate definition, but it doesn't address future deliverability for an e-mail address, which is what marketers usually try to determine with the hard/soft distinction. Also, many e-mail systems don't record transient failures unless they persist for several days, then most are pretty much permanent.

Other people suggest that a soft bounce is a condition such as a full mailbox. Yet such situations are often indicated by SMTP permanent failure codes, as ISPs consider these to be permanent. For example, Yahoo's delivery instructions specifically cite "mailbox full" as a permanent condition that should cause removal of an address from a mailing list.

There are numerous other definitions that vary in precision and clarity. This disagreement on nomenclature results in great confusion, with marketers talking at cross purposes, but it doesn't cause direct harm. The problem occurs when decisions are made based on these definitions.

Many e-mail metrics are based on delivery rate, and where the confusion starts:

  • Deliveries = recipients - bounces

  • Open rate = (opens * 100)/deliveries

  • Click-through rate = (clicks * 100)/deliveries

  • ROI = (revenue - cost)/deliveries

Are bounces defined as all bounces or only hard bounces? Does this include transient failures? Does it include just permanent failures (where the precise definition of what constitutes permanent varies by provider)?

What matters for the metrics isn't an address' future deliverability, but whether the e-mail was successfully delivered. The hard/soft distinction is unnecessary for metrics.

Hard/soft is simply too blunt an instrument. Failures don't split neatly into temporary and permanent. Some may be permanent unless corrective action is taken. A Sympatico block, for example, is permanent, unless you contact the vendor to get it removed. Other failures may be temporary but become permanent if you take the wrong action. An AOL temporary block will expire unless you do something wrong, such as failing to reduce complaints or bounces. Both cases can occur with blocklistings. Transient errors (such as "unable to connect to server") may be permanent.

Furthermore, bounce reason codes aren't universally accurate or descriptive. A database failure can result in a "user unknown" error for perfectly valid addresses. Some sites will return with "system error" for a blocklisting, while others return it for a temporary configuration problem. Some may even return "user unknown" for a blocklisting.

Reliance on automatic classification can cause good addresses to be rejected through overly aggressive hard-bounce culling while bad addresses remain on a list due to failure to cull soft bounces. Leaving bad addresses on a list can be disastrous, resulting in high bounce rates and spamtrap hits as ISPs repurpose addresses that have been undeliverable for a long time.

For these reasons, you must put aside convenient yet misleading concepts like hard/soft and look beyond to the untidy reality that is e-mail delivery. Your marketing metrics and your list hygiene will benefit from the simplification and the complexity this entails.

Until next time,

Derek

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

ClickZ Live San Francisco This Year's Premier Digital Marketing Event is #CZLSF
ClickZ Live San Francisco (Aug 11-14) brings together the industry's leading practitioners and marketing strategists to deliver 4 days of educational sessions and training workshops. From Data-Driven Marketing to Social, Mobile, Display, Search and Email, this year's comprehensive agenda will help you maximize your marketing efforts and ROI. Register today!

ABOUT THE AUTHOR

Derek Harding

Derek Harding is the CEO and founder of Innovyx Inc., a member of the Omnicom Group and the first e-mail service provider to be wholly owned by a full-service marketing agency. A British expatriate living in Seattle, WA, Derek is a technologist by background who has been working in online marketing on both sides of the Atlantic for the last 10 years.

COMMENTSCommenting policy

comments powered by Disqus

Get ClickZ Email newsletters delivered right to your inbox. Subscribe today!

COMMENTS

UPCOMING EVENTS

Featured White Papers

BigDoor: The Marketers Guide to Customer Loyalty

The Marketer's Guide to Customer Loyalty
Customer loyalty is imperative to success, but fostering and maintaining loyalty takes a lot of work. This guide is here to help marketers build, execute, and maintain a successful loyalty initiative.

Marin Software: The Multiplier Effect of Integrating Search & Social Advertising

The Multiplier Effect of Integrating Search & Social Advertising
Latest research reveals 68% higher revenue per conversion for marketers who integrate their search & social advertising. In addition to the research results, this whitepaper also outlines 5 strategies and 15 tactics you can use to better integrate your search and social campaigns.

WEBINARS

    Information currently unavailable

Jobs

    • Interactive Product Manager
      Interactive Product Manager (Western Governors University) - Salt Lake CityWestern Governors University, one of the 20 largest universities...
    • SEO Senior Analyst
      SEO Senior Analyst (University of Phoenix (Apollo Education Group)) - San FranciscoSEO Senior Analyst   Position Summary...
    • SEM & Biddable Media Manager
      SEM & Biddable Media Manager (Kepler Group LLC) - New YorkAs an Optimization & Innovation Manager at Kepler Group, you will be on the bleeding...