Spam still being let through

Hi,

Has anyone seen this before? The spam is being let through, even though 
the score is over 5.

X-Spam-Checker-Version: SpamAssassin 3.1.7 (2006-10-05) on av-1
X-Spam-Status: Yes, score=5.6 required=5.0 tests=AWL,FUZZY_OCR_KNOWN_HASH,
	FUZZY_OCR_WRONG_EXTENSION,HTML_10_20,HTML_MESSAGE,MIME_HTML_ONLY 
	autolearn=no version=3.1.7

Here is the part of the exim configuration which should drop the message

# Reject spam messages with score over 5, using an extra condition.
drop    message = This message has a spam score of $spam_score points
        spam = nobody:true
        condition = ${if >={$spam_score_int}{50}{1}{0}}

I've configured Spamassassin on a central server and set sa-exim to use 
the remote server. Is this likely to cause issues?

Any thoughts?

Cheers
Tim