A news URL takes one of two forms:
news:<newsgroup-name>
news:<message-id>
A <newsgroup-name> is a period-delimited hierarchical name, such as
"comp.infosystems.www.misc". A <message-id> corresponds to the
Message-ID of section 2.1.5 of RFC 1036, without the enclosing "<"
and ">"; it takes the form <unique>@<full_domain_name>. A message
identifier may be distinguished from a news group name by the
presence of the commercial at "@" character. No additional characters
are reserved within the components of a news URL.
'news:' and 'mid:' (and 'cid:') should have the same syntax. In fact,
the only difference between a 'news:' and 'mid:' URL is that
'news:' has an implicit context of 'your netnews' while 'mid:' has the
context of 'your mail'.