On Wednesday, June 4, 2014 6:45:40 PM CEST, Wietse Venema wrote:
You are missing the point. The internal SMTP client does not
look up the recipient MX host. It just gives the mail to the
perimeter gateway.
Therefore, a non-EAI internal SMTP client can send an email reply
to an EAI sender.
I am not missing the point.
Compliant SMTP servers only accept mail to/from EAI addresses if the SMTP
client uses the SMTPUTF8 form of the MAIL FROM command. The SMTP client, in
turn, only uses that form if the origin too used it.
The purpose of this feature is to guarantee that EAI messages don't land in
the mailboxes of incompatible recipients. The relevant effect of this
feature is that in order to send mail to a unicode address, the _sender_
must declare that the message uses EAI. Having 8-bit clean relays on the
way is not enough.
Thus an EAI domain name may show up as xn--mumble in HELO commands.
Yes. I think it's a bad idea to do that. The chance that some SMTP server's
gethostbyname() will return the UTF8 form and the SMTP server then complain
about EHLO/PTR mismatch is too great. But it can happen.
There will be more. I'll just document them and fix them, so I
don't have to spend a lot of time reviewing another version.
Great.
Arnt
