Cc header to myself when following up to mails in my INBOX

[Tassilo Horn <tassilo@member.fsf.org>]

Hi all,

I'm used to hitting `f' or `F' when replying to a mail on one of my IMAP
accounts.  But when I follow up to a mail addressed to myself in
nnimap+Fastmail:INBOX, there's a Cc header to myself inserted, and I
cannot figure out why.

Here's an example followup to my dad:

--8<---------------cut here---------------start------------->8---
To: Winfrid Horn <winfrid.horn@gmx.de>
Cc: Tassilo Horn <thorn@fastmail.fm>
Subject: Re: Laserjet M 1005 in Egglfing
Gcc: nnimap+Fastmail:INBOX
From: Tassilo Horn <thorn@fastmail.fm>
--8<---------------cut here---------------end--------------->8---

What could be the cause of that Cc header?  The message headers of the
mail I'm following up to are those:

--8<---------------cut here---------------start------------->8---
From: Winfrid Horn <winfrid.horn@gmx.de>
Subject: Laserjet M 1005 in Egglfing
To: Tassilo Horn <thorn@fastmail.fm>
Date: Sun, 7 Nov 2010 15:21:34 +0100
User-Agent: KMail/1.13.2 (Linux/2.6.36-gentoo; KDE/4.4.2; i686; ; )
Message-Id: <201011071521.34839.winfrid.horn@gmx.de>
--8<---------------cut here---------------end--------------->8---

AFAIKT, nnimap+Fastmail:INBOX is the only group where Ccs to myself are
generated.

Here are my posting styles and gnus parameter definitions.

--8<---------------cut here---------------start------------->8---
(setq gnus-posting-styles
      `((".*"
         (address "thorn@fastmail.fm"))

        (,(rx (or "nntp+Eclipse"
		  "infko."
		  "nnimap+Uni"))
         (address "horn@uni-koblenz.de")
         (signature th-gnus-uni-signature))

        (,(rx (or (and (opt "de.") (or "comp." "comm.software."))
                  "gnu."
                  "nntp+Gmane:"
		  "nnimap+Fastmail:INBOX.FSF"
		  "nnimap+Fastmail:INBOX.mailinglists."))
         (address "tassilo@member.fsf.org"))

        (,(rx "gmane.comp.printing.ghostscript.")
         ;; Posting requires whitelist keyword "artifex" spelled backwards.
         ("X-Fnord" "xefitra"))))

(setq gnus-parameters
      `(
        (,(rx (or "emacs" "gnus"))
         (gnus-button-emacs-level 10))

	(,(rx "nnimap+")
	 (gnus-use-scoring nil)
	 (gcc-self . t))

	(,(rx "nnimap+Uni:ml/")
	 (gcc-self . "nnimap+Uni:Sent"))

	(,(rx "nnimap+Fastmail:INBOX.mailinglists.")
	 (gcc-self . "nnimap+Fastmail:INBOX.Sent Items")
	 (gnus-use-scoring t))))
--8<---------------cut here---------------end--------------->8---

Any ideas how I can get rid of that self-Cc-ing in that group?

Bye,
Tassilo