That is always an unfortunate circumstance, but is something you should expect to happen periodically when using a shared mail server, even though in most cases with DH the block is not reasonable or justified.
That sounds like a reasonable enough assumption to make, but probably does not take into account other common (and entirely possible, even probable) circumstances. For example, Comcast, AOL, ATT, and others, have given the "spam" excuse on many occasions in the past when "spam" originating from DH was not really the problem at all. Email forwarded by their customers from Dreamhost to their own accounts has routinely been "flagged" as spam originating from the Dreamhost server doing the forwarding, though any "human" moron (as opposed to a "broken" spam filter!) could easily tell Dreamhost was not the source, and that the customer, in effect, "sent it to him/her self".
These same providers have also reacted to the volume of mail arriving at their servers from DH shared-mailservers with the "fuzzy logic" that says, "If this server sent our server that much mail, it has to be spam; let's block it."
In short, these types of blocks can, and do, happen periodically with DH shared mail-servers even if no other user on your shared mail-server(s) has sent any spam.
I believe it would have no effect as long as the mailserver is shared, and it is my understanding that all Dreamhost mail uses these servers, irrespective of your domain being assigned a dynamic static IP address.
That is a completely understandable, and reasonable position to take. That said, Dreamhost's aggressive monitoring of spam in all its forms, their (recently) limited forwarding options, and their continual working with other system administrators to "rehabilitate" Dreamhost servers that have landed on blocklists is likely to be "as good as it gets" with shared hosting.
I would certainly report the particulars of the block you encountered to DH Support; in the past they have had reasonable success in resolving those issues if they are made aware of them.
There is a lot of discussion of these situations scattered through these forums for the past 18 months or so (just search for block email AOL comcast, etc), if you want to get a "bigger picture" of the situation. While I'm not happy about it, I'm afraid this situation is likely to get a whole lot worse before it gets any better