Need help sketching out a dbase/email app

Hello,

I was wondering if someone is willing to lend a hand with an application I'm building that I suspect needs a dbase

The application:
A person sends an email with a picture attached to an email address. Each email is parsed, the attached image is sent to an image manipulation program which processes it and emails back the results.

I want to be able to scale this application up and what I had in mind was to decouple the mail queue from the image processor by using a dbase inbetween. I can then fire up as many image processors as my server supports and use the transaction capabilities of the dbase to prevent them all stepping on each other's toes.

Any thoughts on how make use of a dbase in this setup?

Thanks,
Douglass Turner