NEXT
The internally maintained "current article pointer" is advanced to the next article in the current newsgroup. If no more articles remain in the current group, an error message is returned and the current article remains selected.
The internally-maintained "current article pointer" is set by this command.
A response indicating the current article number, and the message-id string will be returned. No text is sent in response to this command.
223 n a article retrieved - request text separately
(n = article number, a = unique article id)
412 no newsgroup selected
420 no current article has been selected
421 no next article in this group