I'm working on a website and I want to validate that an individual is an employee at one of a large number of companies (probably using their company's email address, which I don't know before hand). The idea being some users are the general public and others are from these companies. And I need some way to authenticate that the users claiming to be employees are being honest while still having a friendly enough UI.

I did an informal survey of people I know and the domains and emails will match in a majority of cases but they might not always match exactly so you might have a company with a website foo.com and an email [email protected] (although foobar.com did redirect back to foo.com).

And while I can easily check that I'm not sure what other variations might be out there (maybe fooLA.com and email [email protected], etc.)