The WG proposal seems to imply taking all IPs out. The discussion has
mostly been about submission.
It seems to me that there are at least three different IPs used, and some
of these are going to be visible regardless of intent.
Ie, there is the submission IPs, there are "internal" IPs, and external
Submission IPs seem like the largest level of risk, and from my gross
understanding of anti-spam, pretty minor. I'm not sure what the current
source levels are, but submission IPs would be most useful in the case of
hijacked account spam or abusive account spam. Presumably, if spam reports
about such are forwarded to the MSP, then the MSP can easily store the
information somewhere other than the easily forged headers and take the
appropriate action. Only if the answer is "they don't take action" would
you need more.
Also, if the previous thread's list of large MSPs inclusion of submission
IPs is correct, then >2 out of the top 3 have already removed them (ie,
only a fraction of Gmail mail has them at this point).
Internal IPs, this hardly seems controversial. If any mail system did
that, not sure if anyone would bat an eye.
External IPs, ie server to server... I guess one may learn "something" if
you can tell which submission server they talked to, we certainly have
servers across the world... but even with 20 odd locations, I doubt that
would be that specific.
So, I would recommend concentrating on submission IPs. I might also
include a recommendation for submission servers to store the IPs for some
length of time to allow for abuse handling, or even to include an encrypted
version in the message.
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