On 3/6/2025 5:07 AM, Richard Clayton wrote:
Yesterday (Wednesday) at $DAYJOB the percentage of mail delivered to a single recipient (rather than 2 or more) was 99.8566% (I feel justified in providing the precision because the total count was many billions)
For that service, is that percentage for mail coming into it, or mail going out from it? If both, what's the percent coming in.
I also note that the chances of email being automatically classified as spam increases with the number of recipients ... it doubles by the time the number of recipients reaches 10.
One of the challenges in this sort of statistical analysis is distinguishing between pure correlation, versus factors that actually are inherent properties of problematic mail.
So, in this case, there is nothing inherently problematic about having multiple SMTP recipients. It well might correlate. But giving that correlation any sort of controlling effect creates collateral damage, for legitimate mail that has multiple SMTP recipients.
That is, the basic approach lets the anti-abuse folk make email increasingly restricted, since the anti-abuse efforts chase whatever the bad actors happen to do, rather than deal with underlying factors.
And much like avoidance training in animals, the avoidance is retained even after the threat its removed. If/when the bad actors move on and no long demonstrate a particular correlation, the restrictions from those previous anti-abuse factors will be retained.
DMARC is a good example of this problem. There are many legitimate uses for having an rfc5322.from field domain name NOT 'align' in DMARC terms. But they are now prohibited. Forever. Not because lack of alignment is inherently tied to problematic behavior, but because it has correlated with it.
d/ -- Dave Crocker Brandenburg InternetWorking bbiw.net bluesky: @dcrocker.bsky.social mast: @dcrocker@mastodon.social
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