Paul Overell wrote:
If we wish to distinguish between <mailbox> and <Mailbox> then
we ought to use different names, not just different case.
"Different case" is the state of the art in 2821 for this term
and <Atom>. A different name would be nice, but what about the
existing references in other RFCs to <Mailbox> ? That's why I
wrote "likely too late".
| Rule names are case-insensitive
Sure, as seen for 2821bis <domain> and 2821bis <Domain>, not to
be confused with a 2822 <domain>. It's not directly possible
to mix the RFC 2821 and 2822 ABNF.
For <Atom> it's very simple, we can just say 1*atext in the few
places where it's used. Rewriting the 2821bis ABNF in a way
that allows to add the complete 2822 ABNF would be a pain, what
about <domain>, <mailbox>, <path>, <local-part>, and so on ?
And while the syntax differs the semantics is almost identical.