Pete Resnick writes:
So, now I'm beginning to get uneasy about using SHOULD/RECOMMENDED in
here. If we want normative language like the above, we should really
just remove no-fold-quote (since quoted-string is already allowed in
the obs- syntax).
Makes sense to me. Particularly since you can look for a long time
before you find no-fold-quote in real message-ids. Standards are
supposed to drop unused features as they advance, right?
How about simply:
Note: There are contexts outside of Internet mail (specifically
Netnews [ref]) where message identifiers containing NO-WS-CTLs,
quoted-pairs, and specials on the left-hand side of the "@"
cause trouble for some implementations. Since messages
sometimes do traverse contexts, avoiding these on the left-hand
side of the "@" may be safest for implementations.
But intuitively I'm more fond of aligning 2822 non-obs syntax with the
syntax most generators use.