You can determine if SURBL is working by viewing the message headers / SpamAssassin report.
This will depend on what settings you have under security->spam engine->spam assassin tab - reporting. We recommend Report is added to headers.
The X-Spam header will contain URIBL_SURBL
Simply add the URL to the body of your test message.
Also make sure you have a file called: \visnetic mailserver\spam\rules\20_dns_surbl.cf
In that file make sure you have one of the following script groups:
header WS_URIBL_SURBL eval:check_spamcop_uri_rbl('ws.surbl.org','127.0.0.2')
describe WS_URIBL_SURBL Contains an URL listed in the SURBL blocklist
score WS_URIBL_SURBL 6 6.831 6 6.752
header SC_URIBL_SURBL eval:check_spamcop_uri_rbl('sc.surbl.org','127.0.0.2')
describe SC_URIBL_SURBL Contains an URL listed in the SURBL blocklist
score SC_URIBL_SURBL 6 6.831 6 6.752
header OB_URIBL_SURBL eval:check_spamcop_uri_rbl('ob.surbl.org','127.0.0.2')
describe OB_URIBL_SURBL Contains an URL listed in the SURBL blocklist
score OB_URIBL_SURBL 6 6.831 6 6.752