Editing Crossposting (section)

==Crossposting in Usenet==
In [[Usenet]], the destination newsgroup(s) for a particular message is indicated in the "<code>Newsgroups:</code>" line. Most commonly, just one newsgroup is specified. For example;

<code>Newsgroups: sci.space</code>

However, it is possible to specify that the message is intended for more than one newsgroup.

<code>Newsgroups: sci.space,comp.simulation</code>

In this case, the message will be visible both in the <code>sci.space</code> and <code>comp.simulation</code> newsgroups. Despite appearing in two separate places, only one message has been posted. This has several advantages.

* A crossposted message takes up less server storage space, and creates less network traffic, than if individual messages had been posted to multiple newsgroups.
* Usenet reader software can intelligently track whether or not the user has already viewed the message in one newsgroup, even though they might currently be looking at another newsgroup. If multiple individual messages had been posted (i.e. the message's content was ''multiposted''), each would appear to be a new unread message in each newsgroup.
* Replies to crossposted messages will be, by default, also crossposted, and so conversations can occur between readers of the multiple newsgroups without any confusion, so long as nobody "breaks the thread" by changing the groups they post their reply to.  This enables readers of one of the newsgroups in the crosspost to provide corrections, etc. to information posted by somebody in a different newsgroup. By adding a "<code>Followup-To:</code>" line a poster can indicate that answers to his post should be posted to another set of newsgroups than those listed by the "<code>Newsgroups:</code>" line.
* It avoids the fragmentation of replies which tends to occur with multiposted messages. It helps to avoid time wasted on writing a reply which has, in essence, been posted on another newsgroup but which the replier has not seen because they do not read that newsgroup or have not yet looked there.

Crossposting is usually practiced when material is relevant and of interest to the readers of more than one newsgroup. However, sometimes it is used maliciously to begin a thread between newsgroups whose readers are likely to have violently differing opinions, in the hope of provoking a conflict. This is a form of [[Troll (Internet)|trolling]].

Crossposting to more than a small number of newsgroups is likely to be counterproductive. A commonly suggested limit is three newsgroups.

Some NNTP servers drop posts which are crossposted to more than a set number of newsgroups, especially if no "<code>Followup-To:</code>" line exists.