My problem is exactly opposite. Dreamhost is hosting my subdomain. I have one domain and two subdomains. One of them is hosted by dreamhost. The other subdomain works fine. The one hosted by dreamhost does not work. I have submitted the appropriate A record and MX record to my ISP's DNS for changes. Using NSLOOKUP reveals that this is reporting correctly. The MX record now points to dreamhosts mail servers. It has been a week since this has propagated and mail coming from the subdomain hosted on Dreamhost still does not come through.
I'm thinking about using the custom MX records feature but do not have much experience with it. Since it does not work right now, I'm not afraid of breaking anything.
This has been going on for two weeks now. I have an ad due out in a magazine in 9 days so timing is becoming crucial. Yes, I do have an open ticket with dreamhost support but I'm becoming desperate.