I misspoke in the meeting about there being no ABNF for plain-text. It
turns out that there is no use of the term plain-text in any ABNF
production. So there does not need to be an ABNF for plain-text.
However, the term "plain text" is not defined anywhere.
Furthermore, the tags that *are* marked as requiring plain text all use
productions that do not permit utf8.
For example, g= is defined in terms of dot-atom:
key-g-tag = %x67 [FWS] "=" [FWS] key-g-tag-lpart
key-g-tag-lpart = [dot-atom] ["*"] [dot-atom]
which is taken from 2822 and is defined to include only the following:
dot-atom = [CFWS] dot-atom-text [CFWS]
dot-atom-text = 1*atext *("." 1*atext)
atom = [CFWS] 1*atext [CFWS]
atext = ALPHA / DIGIT /
"!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "/" /
"=" / "?" / "^" / "_" / "`" / "{" / "|" / "}" / "~"
If we want to extend g= to permit utf8, or any other tag values, we'll
need to do that explicitly and choose a different set of ABNF leaf tokens.
Tony Hansen
tony(_at_)att(_dot_)com
_______________________________________________
NOTE WELL: This list operates according to
http://mipassoc.org/dkim/ietf-list-rules.html