Set up SpamAssassin

Scan incoming and outgoing email for spam. Use a local Unbound for DNS,
so we don't run into blocks for RBL queries.

site-cookbooks/kosmos_email/attributes/default.rb

@@ -1,4 +1,3 @@
 node.default["email"]["domain"] = "example.com"
 node.default["email"]["hostname"] = "mail.example.com"
-# node.default["email"]["user"] = "ray"
-# node.default["email"]["group"] = "email"
+node.default["email"]["report_contact"] = "abuse@example.com"