Editing Posting style (section)

===How much to trim===
Some style guides recommend that, as a general rule, quoted material in replies should be trimmed or summarized as much as possible, keeping only the parts that are necessary to make the readers understand the replies.<ref name="rfc1855"/>  That of course depends on how much the readers can be assumed to know about the discussion.  For personal e-mail, in particular, the subject line is often sufficient, and no quoting is necessary; unless one is replying to only some points of a long message.<ref name="rfc1855"/>

In particular, when replying to a message that already included quoted text, one should consider whether that quoted material is still relevant.  For example:

 >> [Mary:] Shall we meet this afternoon to discuss the
 >> marketing strategy?<span style="color:red">
 >
 > [Peter:] Perhaps, if we can get all the information we need.
 > Do we have the West Coast sales data yet?</span>
 <br>
 The LA office just sent them in.
 Joe

The quote from Mary's message is relevant to Peter's reply, but not to Joe's reply.  The latter could have been trimmed to
<syntaxhighlight lang="md">
 > [Peter:] Do we have the West Coast sales data yet?
 
 The LA office just sent them in.
 Joe
</syntaxhighlight>
On the other hand, in some situations, any trimming or editing of the original message may be inappropriate. For example, if the reply is being copied to a third person who did not see the original message, it may be advisable to quote it in full; otherwise the trimmed message may be misinterpreted by the new recipient, for lack of context.

Also, when replying to a customer or supplier, it may be advisable to quote the original message in its entirety, in case the other party somehow failed to keep a copy of it.