

The section right below shows that it’s obsolete:
A.6.1. Obsolete addressing
Note in the below example the lack of quotes around Joe Q. Public,
the route that appears in the address for Mary Smith, the two commas
that appear in the "To:" field, and the spaces that appear around the
"." in the jdoe address.
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From: Joe Q. Public <john.q.public@example.com>
To: Mary Smith <@machine.tld:mary@example.net>, , jdoe@test . example
Date: Tue, 1 Jul 2003 10:52:37 +0200
Message-ID: <5678.21-Nov-1997@example.com>
Hi everyone.
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And in the spec itself, that syntax is named as “obs-phrase”.
But yes, though obsolete, it is still legal syntax. So I guess I shouldn’t say it “does not conform to the standard”, but rather “just barely conforms to the standard”.





Folding white space is a different issue. It’s the
atom / quoted-stringpart. That’s the standard form of a display name. Meaning if it’s more than one word (separated by white space), it should use the quoted string form. It does listobs-phraseas an alternative, but using obsolete syntax should be avoided when possible.