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Spamhaus answers questions

Lost in all of the DOS attack news this week is that the first installment of Spamhaus answering questions from marketers in Ken Magill’s newsletter.
It’s well worth a read for anyone who is interested in hearing directly from Spamhaus.
One quote stood out for me, and it really sums up how I try to work with clients and their email programs.

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Inbox rates and conversion rates

Jeanne Jennings published an interesting bit of research on open rates and inbox rates at ClickZ recently. Essentially she looked at two different industry studies and compared their results.
The first study was the Return Path Global Delivery Survey and the second was the Epsilon North American Trend Results. What Jeanne found is that while Return Path shows a decrease in inbox placement, Epsilon is seeing an increase in average open rate.

There are any number of reasons this could be happening, including simply different ways the numbers are calculated. I am not sure it’s just a numbers issue, though. Many of Epsilon’s clients are very big companies with a very experienced marketing team. The Return Path data is across their whole user base, which is a much broader range of marketers at different levels of sophistication.
I expect that the Epsilon data is a subset of the Return Path data, and a subset at the high end at that. It does hint, though, that when the inbox is less cluttered, recipients are more likely to open the commercial mail that does get in there.

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Does email have a guarantee of delivery?

A client asked me earlier this week what SLAs ISPs provided for email delivery. The short answer is that there isn’t a SLA and that the only guarantee is that the email will get there when it gets there.
But as I was mentioning this to Steve, he pointed out that there was a recent change in the RFCs for email. In both RFC 821/2 and RFC 2821/2 (the original email related RFCs and the update in the early 2000’s) the RFCs stated that once a receiving MTA accepted an email that that MTA was required to either delivery the mail or generate an asynchronous bounce. While this isn’t a standard SLA, it does mean that a 2xy response after DATA meant the email would either be delivered to the user or be sent back to the sender. Despite the RFC requirements some receivers would still drop mail on the floor for various reasons, sometimes intentionally and sometimes not.
RFC 5321/2, the current SMTP standard, still says that once a server accepts the mail it must not lose that mail ‘for frivolous reasons.’ The RFC goes on to admit, though, that in recent years, SMTP servers are under a range of attacks and dropping mail on the floor is not frivolous in those cases.
 

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