Subject: [Emailcore] Email address local-part equivalence

From: cketti <[email-masked]>
Date: Sun, 4 Apr 2021 18:59:18 +0200

Hi.

RFC 5321 and rfc5321bis-02 contain the following text:

 > For any purposes that require generating or comparing
 > Local-parts (e.g., to specific mailbox names), all quoted forms MUST
 > be treated as equivalent, and the sending system SHOULD transmit the
 > form that uses the minimum quoting possible.

I'm unsure how to interpret this sentence. What exactly is a "quoted 
form"? Are the following three addresses considered equivalent?

[email-masked]
"local"@domain.example
"\l\o\c\a\l"@domain.example

Or do "quoted forms" require the use of a quoted string, i.e. only the 
last two examples need to be treated as equivalent?

Cheers
cketti

---

From: "John Levine" <[email-masked]>
Date: 4 Apr 2021 14:31:23 -0400

>last two examples need to be treated as equivalent?

Good question.  I am fairly sure the intention has always been that all three
versions are equivalent, i.e., unneeded quoting is ignored.

-- 
Regards,
John Levine, [email-masked], Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

---

From: Dave Crocker <[email-masked]>
Date: Sun, 4 Apr 2021 14:11:55 -0700

> versions are equivalent, i.e., unneeded quoting is ignored.

It occurs to me that current language is in a normative form, as if 
there were an alternative.  This actually could be confusing, as well as 
getting into the problematic area of comparison, what with both Unicode 
complexity and SMTP's supposedly ignoring the local-part.

It's worth considering...

OLD:

NEW:

      All quoted forms are equivalent and the sending system SHOULD 
transmit the form that uses the minimum quoting possible.

It might also be worth adding some examples, such as the above, to make 
this concrete.

d/
-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net