Sending an email?

This is easy with LuaSocket's SMTP module:

local smtp = require 'socket.smtp'
r, e = smtp.send {
 from = 'sjdonova@example.com',
 rcpt = 'sjdonova@example.com',
 server = 'smtp.example.com',
 source = smtp.message{
 headers = {
 subject = "my first message"
 },
 body = "my message text"
 }
}
if not r then print(e) end

Spam, unfortunately, has never been easier.

You can also use CDO with LuaCOM.

As for the other end, luaPOP3 provides a library for writing simple POP3 servers.