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Re: [ietf-smtp] Is this a valid Message-ID header ?

Paul Smith <paul@pscs.co.uk> Thu, 05 March 2020 09:18 UTC

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From: Paul Smith <paul@pscs.co.uk>
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Date: Thu, 05 Mar 2020 09:13:24 +0000
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Subject: Re: [ietf-smtp] Is this a valid Message-ID header ?
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On 05/03/2020 04:34, John Levine wrote:
> I read IETF mailing lists on the IETF's IMAP server* and of late I've been
> seeing some awfully funky stuff.
>
> This is an actual Message-ID header in one of the messages in dnsop.
> Is that valid?  Even though the MIME decodes to a an ASCII message ID
> in the <string@domain> format, I think the answer is no.  That's not
> what RFC 5322 sec 3.6 allows.
>
> Message-ID: =?utf-8?q?=3CBN7PR11MB25474DF04998FF3AA9E0B80BC9E40=40BN7PR11MB2?= =?utf-8?q?547=2Enamprd11=2Eprod=2Eoutlook=2Ecom=3E?=

I would say, no, it's not valid.

The MIME encoding of headers is meant to sit on top of RFC 5322. So, 
format rules in RFC 5322 still have to apply BEFORE decoding the headers.

So,

From: =?utf-8?q?B=C3=B3b Smith?= <bob@example.com>

is valid, because that matches the RFC 5322 rules even though, without 
the MIME decoding, it's slightly gibberish. The format is still valid.

But

From: =?utf-8?q?B=C3=B3b Smith =3Cbob@example.com=3E?=

is not valid, because it doesn't match the rules, even though the MIME 
decoded headers will be identical.



-- 


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