My DSPAM filter often include SpamAssasin headers or other metadata and makes decision based on it. As a lot of emails have similar of these, DSPAM starts to mark a lot of valid emails as spam.
Example:
X-DSPAM-Factors: 15,
wyrazami+szacunku, 0.99980,
wyrazami, 0.99980,
szacunku, 0.99980,
DKIM-SignatureTo, 0.96248,
DKIM-Signaturerelaxed, 0.95961,
X-Spam-Reporthas+text, 0.95637,
X-Spam-ReportMessage+only, 0.95637,
X-Spam-Reportonly+has, 0.95637,
X-Spam-ReportMIME+parts, 0.95637,
X-Spam-ReportMessage, 0.95637,
X-Spam-Reportonly, 0.95637,
DKIM-SignatureSubject, 0.95612,
DKIM-SignatureFrom, 0.94339,
Received-SPFhelo, 0.94174,
Received-SPFip+envelope, 0.94148
X-DSPAM-Result: Spam
X-DSPAM-Confidence: 0.9544
X-DSPAM-Probability: 1.0000
Only 3 first come from message body, else is metadata which marked this valid email as spam.