This causes multiple lookups, adding to an already considerable
overhead on DNS. DMP did this too, but I'd gladly not do that
if the information in SUBMITTER is available.
And if it is not?
That's what Received-From: is for.
The LMAP
designs (and MARID) uses an open ended lookup approach with a total
disregard that the majority of the lookups will fail anyway.
Unless you can somehow force all domains handling mail to deploy such a
solution immediately, you're going to get a majority of failures to begin
with. This was hammered to death yonks ago.
It also
ignores another important parameter - RCPT TO:
Where does this enter into it? Unless you're talking to a relay server
(which you can just AUTH / SUBMIT against to bypass MARID anyway - and be
audited in that fashion) or a forwarding server (which is going to provide
SUBMITTER or Resent-From:) I think we can safely assume the recipient
specified here is on the machine you're issuing this command to, anyway.
Using SUBMITTER adds a high cost to changing software.
We have to do this anyway if we're asking sites to use MARID or a MARID-like
protocol. And unless you know these costs you can't tell me it's less
expensive to implement SPF in Sendmail, for example, than CSV or Sender-ID or
DomainKeys or MARID-Core or MARID-Submitter.
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Sometimes it's hard to tell where the game ends and where reality bites,
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