Some people have had a hell of a time installing Composer on a shared DH account, well here's how I did it. I'm going to assume you know what a shell user is and how to use basic terminal.

How to set up MX records for subdomains (subdomain.foobar.com) that are separate from the primary domain and are authoritative when you are a Dreamhost customer. In other words, this is how you set up your Dreamhost configs such that you can send e-mail to subdomain.foobar.com and have it go to a separate mail server or provider from that for foobar.com.