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require 'resolv'
require 'net/smtp'

from = "your-email@example.com"
to = "another-email@example.com"

message = <<MESSAGE_END
From: #{from}
To: #{to}
Subject: Direct e-mail test
This is a test e-mail message.
MESSAGE_END

to_domain = to.match(/\@(.+)/)[1]

Resolv::DNS.open do |dns|
  mail_servers = dns.getresources(to_domain, Resolv::DNS::Resource::IN::MX)
  mail_server = mail_servers[rand(mail_servers.size)].exchange.to_s

  Net::SMTP.start(mail_server) do |smtp|
    smtp.send_message message, from, to
  end
end