Spam with "clean" header

[Gao]

Hi,

I am doing a test: I want have all emails delivered to user's maildir, 
even it is a high score spam. I'll try deliver spam to a pre-exist 
sub-folder "Junk" in the users INBOX.

So I changed MailScanner.conf:
#High Scoring Spam Actions = store
High Scoring Spam Actions = deliver header "X-Spam-Status: Yes"

Then I send a test spam email. It does delivered to user maildir. But 
when I check the header, I noticed there are a line:
X-mydomain-MailScanner: Found to be clean

Also append to the email with:
-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.


Could you please explain to me why it is "clean"? Does it mean a "virus 
scan clean"?

Thanks.

Gao


Here is the whole email:
===================================
Return-Path: <root at cac.mydomain.com>
X-Original-To: gao at mydomain.com
Delivered-To: gao at mydomain.com
Received: by cac.mydomain.com (Postfix, from userid 0)
     id 2D1E8207B708; Thu, 26 May 2016 11:17:16 -0700 (PDT)
Date: Thu, 26 May 2016 11:17:15 -0700
To: gao at mydomain.com
Subject: {Spam?} test spam
User-Agent: Heirloom mailx 12.5 7/5/10
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Message-Id: <20160526181716.2D1E8207B708 at cac.mydomain.com>
From: root at cac.mydomain.com (root)
X-mydomain-MailScanner-Information: Please contact the ISP for more 
information
X-mydomain-MailScanner-ID: 2D1E8207B708.A565A
X-mydomain-MailScanner: Found to be clean
X-mydomain-MailScanner-SpamCheck: spam, SpamAssassin (score=1001.1, 
required 6,
     DCC_CHECK 1.10, FSL_BULK_SIG 0.00, GTUBE 1000.00, NO_RELAYS -0.00)
X-mydomain-MailScanner-SpamScore: 1001
X-mydomain-MailScanner-From: root at cac.mydomain.com
X-Spam-Status: Yes

XJS*C4JDBQADN1.NSBN3*2IDN<add sth here to bypass spam 
check>EN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.