Bruce Lilly wrote:
The rules for encoded-words in header fields are simple and clear:
1. never anywhere in any Received field (it's not clear *why*, but
that's the rule). Of course. that's not a news issue.
2. never in a MIME parameter (2231 extended parameters may be used there)
3. any "word" in a "phrase" (RFC 822 definitions), separated from
adjacent graphic characters by whitespace
4. in a comment, adjacent to an unquoted parenthesis or separated
from other adjacent graphic characters by whitespace
5. in unstructured text ("*text" per RFC 822 definitions)
The last three rules can be compressed to one; they comprise all of
the places where human-readable text (vs. protocol elements) are
located.
Small corrigenda:
for item 2 (which is merely a clarification of 3-5), substitute:
2. never in a quoted-string
change "three" to "four" in the last sentence,
and add "except quoted-strings in a phrase" to the last sentence.