Please, be really, really sparing with this, as the news gateways used for this are usually in a really tenuous position (i.e. being done under the noses of the machine's admin).
post1: <server> ((chain)) . . . postn: <server> ((chain)) post_all 1, ..., n
From the premail doc: One frequently asked question is: how can I follow up on a thread while posting anonymously? This is easy. Find the Message-Id: header field in the post you're responding to, and change it into a References: field in your outgoing mail.
This can easily be done with cut&paste (use screen, it's good for you and has cut&paste that works on ascii terminals).
In theory, you can do normal chaning commands (including nym stuff) as long as the dest is a mail-to-news gateway. I haven't actually got this tested yet, but it follows naturally.