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
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.
And as for what happens inside of an ADMD, I'm afraid I really don't give a
damn what the standards say should or should not be done to addresses
IP addresses within my own infrastructure. I'll forward with rewriting,
discard, or do whatever I like with them as I choose.
_ | Peter J. Holzer | A coding theorist is someone who doesn't
|_|_) | | think Alice is crazy.
| | | hjp(_at_)hjp(_dot_)at | -- John Gordon
__/ | http://www.hjp.at/ | http://downlode.org/Etext/alicebob.html
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