fcc with nnml mail spool

[Roland Winkler]

The following message is a courtesy copy of an article
that has been posted to gmane.emacs.gnus.user as well.

If mail is stored in mbox format, an fcc header allows to keep a local
copy of an outgoing mail message, where (by default) the copy of the
mail message is appended to an mbox file like any external messages.
This way, everything in a thread is naturally kept together for later
reference, the external mail messages plus my replies.

How can one achieve the same thing with the nnml mail spool?  Of course,
there is the bcc header.  But can one also generate local copies of
outgoing mail messages that go straight into one of the nnml mail
groups?

I guess the syntax of the old-fashioned fcc header is not the most
helpful for this.  Instead of an mbox file it would be useful to specify
the Gnus group the copy of the outgoing mail message should go into.
Such a syntax could even work with any other Gnus mail back end.  Or am
I missing something?

I also found the variable message-fcc-handler-function.  But I am not
sure how it can possibly help in the above context.