From http://pobox.com/~djb/proto/immhf/token.html:
An atom is a string of one or more characters terminated by the end
of the field value or by any of these characters: space, tab, @, <,
>, [, left parenthesis, comma, semicolon, colon, dot, double quote.
(Note that adjacent atom tokens must be separated by at least one
comment, space, or tab.)
RFC 822 says the same thing: atoms ``are delimited by the
self-delimiting symbols and by linear-white-space.''
Charles Lindsey writes:
I was working from the syntax in DRUMS
Not a good idea. The ABNF+822bis syntax is an untested computer program
in a weak, error-prone programming language.
---Dan