On 25/May/10 03:55, Steve Atkins wrote:
On May 24, 2010, at 6:38 PM, John Levine wrote:
Refusing signups from those domains is probably a bit extreme, though.
What about a warning at signup time if a "discardable" ADSP record is
found for the registrant's domain?
That doesn't help. In the IETF's scenario, domain A sent mail which
was marked discardable to the list, and recipients at domain B were
rejecting it and the people at B got bounced off the list. I'd have
to squint awfully hard to come up with an argument that it is wrong to
reject unsigned discardable mail at SMTP time.
I think that Murray was suggesting that in addition to rejecting all
mail from domain A it would be polite to also warn anyone from
domain A who subscribes to the list that their mail would be
rejected (which seems good UX design to me).
That warning is an /alternative/ to refusing signups. The BCP
distinguishes between participating and non-participating MLMs, and
that warning belongs to the former kind. I'd expect a participating
MLM has also fixed the double-footer problem, while most lists have no
problems with double subject-tags. Hence, the warning may merely
recall that posts from the discardable address will be rejected unless
they include the correct footer, and the subject-tag appears exactly
once, the latter especially for new posts. (Notice that such practice
is may also help to avoid light-minded posts.)
We cannot suggest anything to DKIM-unaware MLMs. Hence, the "refuse
signups" option, that would apply in this case, has to be put through
by subscribers themselves.
Since ADSP causes problems for innocent bystanders, I think it's
reasonable to decline A's mail in the first place. This is doubly
true since the ADSP RFC rather specifically says that you shouldn't
mark a domain discardable if its users send mail to lists.
It causes no problems at all to innocent bystanders in that case - the
recipient at domain B is a willing participant who has chosen both
to pay attention to ADSP and to respond to it by rejecting, rather than
discarding, mails labeled "discardable".
That user will probably contact postmaster(_at_)B and ask for the relevant
list to be whitelisted. If a list's operators seek such explicit
whitelisting at their subscribers' MXes, then they might want to
leverage ADSP that way.
BTW, is "discard" exactly synonym with "drop"? I'd recommend dropping
mail only in cases of negligibly low FP rates _and_ high risk, e.g.
viruses. Deliver-as-junk is used as a makeshift, and I tend to
associate "discardable" with such behavior. Is that what RFC 5617
means by it?
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