Good idea, thank you!
I checked this, and it seemed the messages are indeed checked by my server, at least for spam - the header shows the following lines
X-SoftScan-Status: clean (virus: 1/1/1/1, spam: 1, paranoid: 1/1)
X-Secure-TLS: Yes, message received through TLS by some.machine.xx (AES256-SHA)
X-Cloudmark-Score: 0.000000 []
X-Spam-Status: No, hits=0.0 required=5.0 tests=
X-Spam-Check-By: my.server.xx
X-pstn-levels: (S:24.80035/99.90000 P:95.9108 )
X-pstn-settings: 3 (1.0000:1.0000) s gt3 gt2 gt1 p
X-pstn-addresses: from <mailad@myserver.xx> [567/24]
But the number seemed a little odd, so I checked the spamd log - it contains these lines
2006-12-29 20:11:08.466646500 [6530] info: spamd: connection from localhost [127.0.0.1] at port 45448
2006-12-29 20:11:08.491648500 [6530] info: spamd: checking message <4595684A.1060408@myserver.xx> for qpsmtpd:1005
2006-12-29 20:11:11.311352500 [6530] warn: pyzor: check failed: internal error
2006-12-29 20:11:11.374351500 [6530] info: spamd: clean message (0.0/5.0) for qpsmtpd:1005 in 2.9 seconds, 595 bytes.
2006-12-29 20:11:11.374363500 [6530] info: spamd: result: . 0 - scantime=2.9,size=595,user=qpsmtpd,uid=1005,required_score=5.0,rhost=localhost,raddr=127.0.0.1,rport=45448,mid=<4595684A.1060408@myserver.xx>,autolearn=disabled
2006-12-29 20:11:11.578851500 [6373] info: prefork: child states: II
The line with "check failed: internal error" seems a little worrying?