The email system doesn't like senders saying a message is from "Instant Booster" because that is not an email address. It will then normalize that field by converting the barewords to email addresses - using the server name as the mail host. So you can't really go by the "From" header, you have to look at the other headers to see what machines are involved in passing the message. It might not have originated at DreamHost.
openvein.org -//- One-time [color=#6600CC]$50.00 discount[/color] on [color=#0000CC]DreamHost[/color] plans: Use ATROPOS7