Dana,
If I correctly understand your note on this subject, someone is confused.
ISO 639 really is "codes for names of languages". If my memory serves
me correctly, it even makes the formal distinction between written forms
(its subject matter) and spoken ones, but I could be wrong. The country
code list is ISO 3166.
While the 636 list clearly does not cover all of the languages of the
world (by any definition), the originating ISO TC and SC--who are of the
librarian persuasion, not the linguistic one--claim that it does cover
all of the languages in which literature that ends up in books and libraries
is produced. That list would probably be a close approximation to a superset
of the languages that are likely to appear in "conventional message"
electronic mail; specialized markup remains a likely requirement for
special cases.
john