blocking email from Vietname is not working...

[Screaming Eagle]

I have this in local.cf file:
describe BL_COUNTRY_VN_1 Mail client in Vietnam
header   BL_COUNTRY_VN_1 eval:check_rbl('vietnam', 'vn.countries.nerd.dk')
score    BL_COUNTRY_VN_1 8.0
tflags   BL_COUNTRY_VN_1 net

Whis is it not working? I get an email from Vietname, and the score is 0. See below. Any idea?

X-Spam-Status: No, score=0.0 required=8.0 tests=BAYES_50 autolearn=ham 

        version=3.1.0

X-Spam-Level: 

Received: from 4CFD6728 (adsl.hnpt.com.vn [203.210.231.8] (may be forged))



Thanks.