Php/Joomla: filter geolocation-tagged data, send in personalized email

You might have seen that MailChimp has new features to GeoTag users (mark their location) and send a newsletter to all users within 0-50 miles of a fixed point. Their system knows where users are located (via reverse IP lookup), and you can send a newsletter to all people within 50 miles of Downtown Los Angles (for example).

I'm interested in doing the exact oposite -send each user an email with all geo-tagged content that is within X miles of their location.

I have geo-tagged content, and I also know where my users are located (via t开发者_运维知识库heir Zip Code). I need to generate these emails on the fly for very large send-outs (1,000-50,000 emails per week).

So! I need some advice about different methods for generating these emails without destroying my server. There will be a lot of filtering and/or processing, or is there a better way? What types of frameworks/tools/services are out there to help?

My server works with PHP 5.2+ and Joomla!, but I'm not opposed to setting this up with another server working with a copy of the MySQL database and another environment written in Java, etc.

In the end, the easiest way to do this was to not use Joomla and instead write a custom code. The job is broken up over several servers, to handle the volume.