spam: threshold 5.0 + 4 DNSBL servers

stalwart_config.toml

@@ -83,6 +83,34 @@ default = true
 "47.197.93.62" = true
 
 [spam-filter.score]
-spam = 8.0
+spam = 5.0
 discard = 0
 reject = 0
+
+[spam-filter.dnsbl.server.spamhaus_zen]
+enable = true
+scope = ip
+lookup = zen.spamhaus.org
+tag = RBL_SPAMHAUS_ZEN
+score = 8.0
+
+[spam-filter.dnsbl.server.spamhaus_dbl]
+enable = true
+scope = domain
+lookup = dbl.spamhaus.org
+tag = URIBL_SPAMHAUS_DBL
+score = 6.0
+
+[spam-filter.dnsbl.server.spamcop]
+enable = true
+scope = ip
+lookup = bl.spamcop.net
+tag = RBL_SPAMCOP
+score = 5.0
+
+[spam-filter.dnsbl.server.barracuda]
+enable = true
+scope = ip
+lookup = b.barracudacentral.org
+tag = RBL_BARRACUDA
+score = 5.0