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Aug 06, 2007

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DJ Waldow

Tamara -

We just posted on this issue on Monday - http://blog.bronto.com/bronto_updates/2007/08/31-flavors-of-b.html

dj at bronto

Tamara Gielen

Thanks for the insights Maarten. It sounds pretty tricky indeed!

Maarten Oelering

As the author of email marketing software I know how hard it is to give general guidelines on bounce management. To decode, analyze and classify the hundreds of different bounce mail formats is a complex task. Furthermore, the bounce code or description in the bounce mail is sometimes inconsistent or just incorrect.

The famous two categories, "hard" and "soft", for which many use different definitions, is vague concept and a generalization which should not be used to base any business logic on. On the other hand, trying to be very specific about the bounce reason is also problematic. When the bounce mail is not clear or misleading, invalid addresses may bounce forever or valid addresses may be thrown out of the list.

I think the best "guideline" is to properly filter out all the invalid recipient addresses (mailbox unavailable, user unknown, invalid recipient, etc.), and remove them from the list after one mailing. All other bounces with a code "5" (not delivered after one or more retries) should be removed from the list as soon as the following conditions (which are also specified by the ISIPP) are both met:

- at least three consecutive bounces have occurred, and
- the time between the first bounce and the last bounce is more than 15 days

By "generalizing" this way, a good balance is achieved between the risk of getting into deliverability problems, and the risk of misinterpreting inaccurate bounce mails. For more background I would recommend to read the articles on bounce management by Derek Harding on ClickZ.

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