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canopic jug writes:

On his blog, Peter N. M. Hansteen sometimes writes about the problems with getting certain mail service providers to up their game. This time his post provides the details on how a particularly large service not only fails at SMTP sender verification but also at many other tasks necessary for professional mail hosting.

Whenever I encounter incredibly stupid and functionally destructive configuration errors like this I tend to believe they're down to simple incompetence and not malice.

But this one has me wondering. If you essentially require incoming mail to include the contents of spf.outlook.com (currently no less than 81 subnets) as valid senders for the domain, you are essentially saying that only outlook.com customers are allowed to communicate.

If that restriction is a result of a deliberate choice rather than a simple configuration error, the problem moves out of the technical sphere and could conceivably become a legal matter, depending on what outlook.com have specified in their contracts that they are selling to their customers.

One takeaway is that spam-fighting decisions from decades past have left us with technologies that have led to the centralization of mail on fewer and fewer providers. As such it is increasingly difficult for even skilled professionals to operate their own mail hosting smoothly.

Source : A Life Lesson in Mishandling SMTP Sender Verification

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