Yes, the solution you have proposed is possible, and you can use sub-domains rather than sub-directories in the scenario you have described (e.g. company.emailjobs.com rather than www.emailjobs.com/company).
You can configure IIS with a wildcard sub-domain, so that all sub-domains bind to a single web site, and then use a regular expression in your code to determine the text for the sub-domain in an HTTP Request. Your regular expression might look something like this:
^(?<subdomain>\w+)\.emailjobs\.com$</subdomain>