All,

I'm in the process now of building a SaaS tool that allows network admins to generate notification emails to the members of the end-users of our platform (among many many other things). I'm running into a bit of an "out of my expertise" wall, as I know there are a lot of variables involved with configuring an application that can:

1. Run in a distributed way via load balancing and still--
2. Leverage a single mail server for sending notification emails
3. Process unsubscribe requests
4. Avoid any ISP blacklisting in the process.

If anyone has the time and has done this before, I'd love if you could walk me through the A-Z of best practices both from a configuration perspective and an execution perspective for generating these emails (anything from necessary DNS settings to ideal SMTP setup and configuration)

Currently, our application generates email via Google Apps using the PHPMailer class. While this works well, it doesn't queue messages (potential for timeout problems if any of our clients amass a very large list of end-users), and Google limits the amount of allowed generated email messages to 500/day.

I know this is a lofty question, but any guidance you could provide would be smashing and a big help as we work through this hurtle in our beta development stage.

Thanks!