managing subdomains cookbook
kitt: Pointer: google for subdomain rewriteIf you are using apache, and mod_rewrite, you can set up rewrite rules for subdomains.http://www.webmasterworld.com/forum92/4640.htm suggests  rewrite rules to redirect a subdomain to a page/app on the main domain.Then, use a domain wild card to point everything to your main www.example.com host (create an A record (HOST) to point * to your IP address).Now, all example.com subdomains (hosts) will go to the A record IP address, which will be redirected to the program/pages/urls you expect.Next, have the customer modify their DNS to point to your IP address.  If you want, you can do the request yourself to their current ISP, to update the domain's DNS, if they're keeping their email with the ISP.  If they don't, and you're controlling their email, too, go with Google's hosted email.Now, this unknown domain is coming to your IP address.  If you're using apache, set up the domain to go to the redirected domain.  Easy way to do that is to set up a server alias, or have a virtual host that answers for everything:<VirtualHost *:80>
</VirtualHost>One way to do it, at least.