On the Spindrop blog today, Dave Dash posts about how he used the sfDoctrine plugin functionality to match allowed email domains for their website's registration.

I'm a co-founder at an online finance web site and I'm in charge with building out the site. Our rollout strategy is to let a a handful of companies at a time, so we're limiting registration based on your company's email address. I decided to follow the bandwagon and use PHP Doctrine.

His example code sets up the company information in objects that are validated against from a validateSignup (and match) function in the application.