Junk filter not placing x-spam-score on all emails

Hello all,
I’ve noticed that some of the spam that gets through to my mailbox does not have the spamassasin headers necessary for the filtering system to place it in quarantine. Is there a reason why spamassasin would not add its headers(x-spam-score specifically) on some of the emails but would on others?
I would say that approx. 15-20% of all spam that I have received so far did not contain the x-spam-score header.
I’ve a stock configuration of the junk mail filter provided by DH.

Any ideas in this matter would be appreciated.


Wow, none of my e-mails have the spam score in the header. NO matter what values I set for the tag and quarantine fields.