posting n.
Noun corresp. to v. post (but note
that post can be nouned).
Distinguished from a `letter' or ordinary email message by the fact that it is broadcast
rather than point-to-point. It is not clear whether messages sent
to a small mailing list are postings or email; perhaps the best
dividing line is that if you don't know the names of all the
potential recipients, it is a posting.