Configuring personal IP address/domain in Actionmailer

I have configured localhost for sending emails from my RoR application over port 25. But, now, I want to use personal IP address/domain for sending emails instead of localhost port 25. Below is small piece if code for my present setup.

ActionMailer::Base.sendmail_settings = {
  :address              => "localhost",
  :port                 => 25,
  :domain               => "www.abcexample.com"
}

Here are my two queries:-

1. Can I use some particular IP address which is being used for my domain?
2. Is it possible if I can configure a secondary domain/IP to avoid failover situation i.e. one server fails, the email can be automatically routed via another configured domain/IP in action mailer?

Please help and guide on this.

Thanks in advance.