Here is the announcement DreamHost sent out
Over the weekend, the Junk Filter found a new and interesting way to break. One of the filter
machines continued to accept mail and appeared to be operating fine, but was holding mail.
The problem first surfaced late on Friday and were resolved early this morning. No mail was
lost, only delayed. Because only one machine was affected, about half the mail going to your
domains will have gone through, and half delayed.
We've fixed the issue and improved our monitoring systems to detect situations like this in the
future. Our apologies for the delay.
Happy Dreamhost Junk Team