On 10/6/19 10:14 AM, Arnt Gulbrandsen wrote:
On Sunday 6 October 2019 14:13:38 CEST, Keith Moore wrote:
Regarding the use of IDNs, the easiest way to address this is to not
use IDNs as the targets of MX records - since users don't generally
see the MX records anyway.
Which is a good idea for another reason — the MX target is generally
the same as or similar to the name used as EHLO argument, and EHLO is
issued before the sender knows whether the received supports SMTPUTF8.
I can't find any justification at all for ever using the UTF-8 form of
an IDN in EHLO. IMO it should be a MUST NOT.
Ahem. See RFC 6531, sec 3.7.1.
But I don't know whether it's reason enough to get a non-IDN domain.
I should hope not. Any mail server that doesn't properly handle ASCII
mail to and from addresses that contain A-labels is pretty badly
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