[ietf-smtp] Are A-label and U-label addresses supposed to be equivalent ?

John R Levine <johnl@taugh.com> Sun, 12 July 2020 02:30 UTC

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Date: 11 Jul 2020 22:30:42 -0400
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From: "John R Levine" <johnl@taugh.com>
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Subject: [ietf-smtp] Are A-label and U-label addresses supposed to be equivalent ?
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Let's say I had these two addresses, which are the same except that one 
has a U-label and the other has the equivalent A-label.  They're both 
non-ASCII addresses since the mailbox name is in Chinese

用户1@后缀.services.net
用户1@xn--fqr621h.services.net

Presumably if you're sending mail to those addresses, you should send them 
to the same place.  But on the final delivery MTA, is that one address or 
two?  Different mail software implement it differently.

Looking at RFCs 6530 and 6531 I get the impression the authors assumed 
they'd be the same but I don't see anywhere it explicitly says so.

Regards,
John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly