We have installed the adminstration kit to an SBS 2003 server and have used the Kaspersky Exchange 5.5 module for anti-spam. This does not detect any spam. Spam only gets detected at the client by Kaspersky Outlook plug in.

Whilst this works I would prefer to deal with spam at the server level.
We use the pop3 connector to collect mail because our client uses the domain widely and many outside workers have pop3 boxes. These should not have access to the network so our hands are tied to pop3 collection. (Besides that if we could use smtp mail we would probably use external spam filters anyway!)

I suspect the pop3 collection is why the spam module is not detecting anything as I beleive the pop3 connector bypasses some of the delivery route.

I have thought about using a 3rd party collector like pop con which I think better mimics smtp delivery.

Is this a known issue and is there a way to solve it?

Thanks in advance

No, spam check works only with SMTP not POP3.

Intelligent spam recognition technologies.
The application scans all messages that are transferred to the Microsoft Exchange Server via the SMTP protocol for spam attributes based on filtering by formal attributes (e.g., email and IP addresses, message size, headers, etc.). It also analyzes message contents and attachments using intelligent technologies, including unique graphical signatures, which help detect spam in image form.