You might want to look somewhere besides DreamHost for the email. Besides the issues with email in general (see for example, https://discussion.dreamhost.com/thread-146427.html), DreamHost has told me in the past that the only supported configuration is if they are the nameserver. DreamHost insists they might change servers or IP addresses without warning, and if DreamHost is not the nameserver for your DNS, you won’t know about those changes until you realize your email/etc. is broken.
I went ahead and took the risk of moving the nameserver away from DreamHost, and they’ve not actually changed the server or IP, so it’s ended up working out, so far. I have automated monitoring on it, though, so I’ll know if it does change. (Ironically, they did change the IPs for a different domain that DreamHost was the nameserver for, and they screwed up so something didn’t propagate and that site broke anyway.)