On Jul 31, 2016, at 9:31 AM, Peter J. Holzer
<hjp-ietf-smtp(_at_)hjp(_dot_)at> wrote:
On 2016-07-31 08:39:51 -0700, Ned Freed wrote:
I asked a similar question about CNAME records about 2 years ago, and
the consensus was that a relaying MTA must not change the recipients
address while the receiver MTA may treat the address any way it pleases.
When does this case even arise?
Pretty rarely, I guess. And it should almost always be avoidable.
If I relay on a message to an address involving some random IP
literal, that's pretty much the definition of an open relay.
I don't think it makes a difference whether the relay relays to random
domain names or random ip addresses. Outbound MTAs are generally
expected to send mail anywhere. But they aren't open because they
restrict who can send.
In fact about the only relay case left that crosses between ADMDs is
secondary MXes, and that doesn't apply to IP address literals by
definition.
Well, I could subscribe to this list as
<hjp-ietf-smtp@[2001:15c0:65ff:8763::d]>. I bet I would get less spam at
this address than at <hjp-ietf-smtp(_at_)hjp(_dot_)at> ;-). Not sure whether
the
mailing list software would handle that, though.
Probably (mailing list software would not handle that), because that is not
even valid syntax (to say nothing of the other RFC 5321 text).
It should be:
<hjp-ietf-smtp@[IPv6:2001:15c0:65ff:8763::d]>
See RFC 5321 section 4.1.3.
Sean
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