On 2021-02-10 12:08, Andrew C Aitchison via mailop wrote:
On Wed, 10 Feb 2021, Dave Crocker via mailop wrote:
The much larger address space makes it too easy for a bad actor to
jump around and, therefore, not develop a bad reputation associated
with the address. So non-history features are made more strict.
My recollection is that when IPv6 mail services started being available
the received wisdom here was that any IPv6 blocks (this was before
talk of reputation was common) should be at the /64 level (cf /32 in
IPv4) on the assumption that ISPs would give each end user a /64.
Is that still reasonable advice, if you *are* blocking or scoring
IPv6 addresses (presumably as well as domain/host names) ?
Unfortunately it is complicated by the fact that you can't count on IP
allocations to happen at any particular subnet point, especially when
you consider VPS environments, and similarly, providers will typically
give out a new and larger range when you ask.
Given this, it makes it a lot harder to track any sort of negative
history as you can assume a malicious sender will just jump to new IPs.
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