Why has SpamAssassin so much problems with this kind of message

[Cecil Westerhof]

I think I get almost a year almost daily messages with this kind of
header:
    Return-Path: <i...@vlanmail.be>
    X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on munus.decebal.nl
    X-Spam-Level: **
    X-Spam-Status: No, score=2.9 required=3.0 tests=BAYES_80,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,FROM_EXCESS_BASE64,HTML_MESSAGE,RP_MATCHES_RCVD
        autolearn=no autolearn_force=no version=3.4.1
    Delivered-To: …
    Received: …
    X-Virus-Scanned: Debian amavisd-new at cloud01.kovoks.nl
    Authentication-Results: cloud01.kovoks.nl (amavisd-new); dkim=pass
        header.i=@vlanmail.be
    Received: …
    Received: from ms087.vlanmail.be (ms087.vlanmail.be [37.58.43.87])
        by … (Postfix) with SMTP id 365BC16808
        for …; Sun,  5 Nov 2017 09:25:03 +0100 (CET)
    DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=vlanmail.be; s=sim; i=@vlanmail.be; h=message-id:from:to:
        subject:date:reply-to:mime-version:content-type; bh=XtMJ3izO2lWo
        5An6HMCFpeyDtfvMBO9ooY1MmNGmmXQ=; b=N8VZWvVTfocrtirzYIPRx7vKmzBO
        B6dBLJaks3ElmXFY2T6n7EcIJVEf1mt2GY6j+W0ygbc6DaoClwiOuTzNgotp0Da4
        r9B/7t4rU3tJS/e6lczEJ4LUUJEESVJpRmDkrq9qBrFYp9UZbW/4vzXojDf1X7bQ
        Vr9KPh7yT4tKnVs=
    Message-ID: 
<171105090150.sim_40ltogj_nmxc%2bxy6leeofd0mbcxu_gpwnuulrvadl6xwzwjfm1e8lz9aizvhtai7wgz1udkjolipopq0ynkadryvcnb...@ms087.vlanmail.be>
    From: =?utf-8?B?QXV0b3ZsYW4uYmU=?= <i...@vlanmail.be>
    To: <i...@decebal.nl>
    Subject: 
=?utf-8?B?QWNodGVydm9sZ2luZyB2YW4gZWVuIGtpbmQgLyBIaWogcmlqZHQgemljaHpl?=
        =?utf-8?B?bGYgb212ZXIgLyBHZXZhYXJsaWprZSBidXNyYWNlIC8gSmVmZmVyc29uIGdl?=
        =?utf-8?B?Y2FyamFja3QgLyBDYW1hcm8tY3Jhc2g=?=
    Date: Sun, 05 Nov 2017 09:01:50 +0100
    Reply-To: =?utf-8?B?bm9yZXBseQ==?= <nore...@vlan.be>
    X-MA-Reference: 
SIM_40lTOgJ_nmXC%2BXy6LEeofd0mBCxu_gPwnUuLrVADL6xWzwjFM1E8lz9aiZvhtai7wgZ1uDkjolIpoPQ0YnkaDryvcNBuxf
    X-MA-Instance: 
SIM_40lTOgJ_nmXC%2BXy6LEeofd0mBCxu_gPwnUuLrVADL6xWzwjFM1E8lz9aiZvhtai7wgZ1uDkjolIpoPQ0YnkaDryvcNBuxf.5d2bd9318cf5475e12f554877d153c3b
    MIME-Version: 1.0
    Content-Type: multipart/alternative;
        boundary="----=_NexPart_000"
    X-accepted: Decebal

Any idea why SpamAssassin has so much difficulty recognising this as
spam?

Everytime I get a message that is spam and not recognised as such I
put it in a directory SpamNotFound. And this is processed with:
    if [[ mailToProcess -gt 0 ]] ; then
        echo "${mailToProcess} berichten moeten worden verwerkt"
        mkdirIfNotExist ${toProcessDir}
        mkdirIfNotExist ${processedDir}
        mv ${newDir}* ${toProcessDir}
        error=0
        learned=0
        notLearned=0
        for i in $(/bin/ls -A ${toProcessDir}) ; do
            set +e
            message=$(spamc -L ${typeStr} <${toProcessDir}${i})
            errorCode=${?}
            set -e
            case ${message} in
                'Message successfully un/learned')
                    let "++learned"
                    ;;
                'Message was already un/learned')
                    let "++notLearned"
                    ;;
                *)
                    let "++error"
                    case ${errorCode} in
                        98)
                            echo "${i} was te groot om te worden verwerkt"
                            ;;
                         *)
                            echo "onbekende fout (${errorCode})"
                            ;;
                    esac
                    ;;
                esac
        done
        echo "learned:     ${learned}"
        echo "NOT learned: ${notLearned}"
        echo "error:       ${error}"
        mv ${toProcessDir}* ${processedDir}
        (( ++processedDirs ))
    else
        echo Geen mails gevonden
    fi

And typeStr is of-course spam in this case.

It is almost solved. Sometimes it even gets into spam, but I am just
curious. And maybe it can help to make SpamAssassin better.

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof