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Re: [ietf-smtp] EAI and SMTP mail

2019-10-06 11:37:11
In article 
<5dccf908-f9c2-ae85-4835-cb107ba34105(_at_)network-heretics(_dot_)com> you 
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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