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Re: I-D Action:draft-klensin-rfc2821bis-10.txt

2008-04-15 12:48:03

sm(_at_)resistor(_dot_)net writes:
Not necessarily. That host may apply a different policy for mail coming through the other MX hosts. Otherwise, it would cause backscatter. BTW, the problem may be applicable to IPv4 as well.

Oh wait, I misunderstood what you're saying. And you probably misunderstood me. doesn't have an IPv6 MX, so the only way to deliver mail to it is to open an IPv4 SMTP connection.

Suppose I have only an IPv6 address and want to send John mail (sorry to pick on you, John). I open an IPv6 connection to my ISP's smarthost and send some mail from my address to a address. My ISP's smarthost has an IPv4 address, so it opens an IPv4 connection to the best reachable MX for The connection from my ISP's smarthost to the MX is what I pasted, and where the problem shows up.

And the text I think should be there would be a sentence like this in sections "Note that the reverse-path may be reachable only via IPv6, even if the SMTP connection uses IPv4", possibly with some emphasis to point out that perfectly valid 2821 code/configurations don't support this. would need similar language for "forward-path".