Summary

Network tests allow a site to benefit from other sites reporting email relays and spam-advertised websites. SpamAssassin includes support for RBLs and SURBLs. The latter provide a promising new technique against spam, which works by detecting the URIs that are advertised in spam emails. RBLs, Razor, Pyzor, and DCC are email comparison systems. DCC is considered the most effective. These tests can be used together and most settings are configurable on a site-wise or per-user basis.