Subject: Re: [Jmap] Decoding of unknown headers

From: Arnt Gulbrandsen <[email-masked]>
Date: Fri, 22 Dec 2017 16:58:51 +0000

[email-masked] writes:
> I think RFC 6530 explictly talks about downgrading domain name 
> to punycode and encoding of local part when the receipient 
> server do not support SMTPUTF8. 

No, it talks about downgrading when the recipient does not support EAI. It 
never even mentions punycode.

Arnt

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From: Arnt Gulbrandsen <[email-masked]>
Date: Fri, 22 Dec 2017 17:33:56 +0000

I wrote:
> No, it talks about downgrading when the recipient does not 
> support EAI. It never even mentions punycode.

Maybe that needs a bit of elaboration.

6530 doesn't say "you can encode header fields using punycode when you send 
mail to recipients whose software apparently doesn't support SMTPUTF8", in 
much the same way as it doesn't say "you can encode header fields using 
rot13 when you send mail to recipients whose software apparently doesn't 
support SMTPUTF8".That's because 6530 cannot assume that such recipients 
have any way to decode either. Legacy software doesn't do either rot13 or 
punycode decoding.

What 6530 does talks about is software that DOES support SMTPUTF8 and 
related extensions.

But even for that soft of software there's nothing about punycode support 
in header fields. For example, look at 6855, It could have said that the 
when the IMAP server handles FROM/TO/CC/... search keys, it must/should 
decode possible punycode decoding. But it does not say that. It makes no 
such requirement. It doesnn't even reference the punycode RFC.

Perhaps you (Ayjay) are confusing 6530 etc with the experimental and 
deprecated RFCs?

Arnt