It looks like that the mailbox is toa@ngāpukapuka.nz which is EAI address on which mail is received from mailchimp however when the sender tried to deliver to UA list, it was downgraded to its punycode. 

thanks. 
 
Dr. Ajay DATA  | Founder & CEO 
Get email id like अजय@डाटा.भारत in your own language,
visit www.xgenplus.com 

From: Arnt Gulbrandsen <arnt@gulbrandsen.priv.no>  MailId : [79911014]
To: ua-eai@icann.org
Subject: Re: [UA-EAI] MailChimp - Is it EAI Ready?
Date: 28 Mar 2018 03:21:23 PM

toa@xn--ngpukapuka-vfb.nz writes:
>  Today I received a message in my toa@ngāpukapuka.nz mailbox
>  from a sender through MailChimp!

IIRC at least four other companies in the same sector are too, namely
Elastic Email, Mailgun, Return Path and SMTP2Go. (Some of those would
disagree that they are in the same sector — there`s email and email.)

JFYI, the message you sent isn`t an EAI message, it`s a legacy message that
happened to use "xn--" in the domain. If you look at the Received fields,
you can see it was transmitted by the initial sender via "smtp", not one of
the protocol types specified in RFC 6531 section 4.3. For this reason, the
top line of this message is actually an accurate rendering of the address
according to your instructions (which I expect do not match your
intention).

Arnt

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