ietf-smtp
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Re: RFC 5321bis / 2821ter

2009-01-26 15:46:27

At 10:17 26-01-2009, Jeff Macdonald wrote:
Doesn't the above also allow the NAT IP as well?

Answering questions involving NAT or SLUT66 [1] is tricky as there may not be any right answer.

There isn't any mention in RFC 5321 about whether IPv4 addresses excludes the ranges of IP addresses defined in RFC 1918. I cannot find a reason to add that to the specifications as SMTP is not restricted to the Internet or public routable IP addresses only.

Some people may argue that the SMTP client cannot be identified if it uses a RFC 1918 IP address in an address literal to communicate with a SMTP server on the Internet. For operational reasons, it's better for such hosts to relay through a smarthost using SUBMIT.

Regards,
-sm

1. http://www.ietf.org/mail-archive/web/behave/current/msg05046.html
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