Updated Lua Examples (markdown)

Lua-Examples.md

@@ -1,5 +1,31 @@
+**Warning**: Lua support in Inbucket is still in a preview state, please expect the API and features to evolve before a full release.
+
 By default Inbucket will load `inbucket.lua`, but you may use the `INBUCKET_LUA_PATH` environment variable to change that.
 
+## Event trigger: before mail accepted
+
+This event fires when Inbucket is evaluating an SMTP "MAIL FROM" command.
+
+Denies mail that does is not from james*@example.com:
+
+```lua
+function inbucket.before.mail_accepted(from_localpart, from_domain)
+  print(string.format("\n### inspecting from %s@%s", from_localpart, from_domain))
+
+  if from_domain ~= "example.com" then
+    -- Only allow example.com mail
+    return false
+  end
+
+  if string.find(from_localpart, "james") ~= 1 then
+    -- Only allow mailboxes starting with 'james'
+    return false
+  end
+
+  return true
+end
+```
+
 ## Event trigger: after message stored
 
 Prints metadata of stored messages to STDOUT: