posts the article to both the groups sci.space and
comp.simulation. It's usually safe to crosspost to up to three
or four groups. To list more than that is considered "excessive
noise."
It's also suggested that if an article is crossposted a
Followup-To: header be included. It should name the group to
which all additional discussion should be directed to. For the above
example a possible Followup-To: would be