I wonder if it has anything to do with this:
If you have customized your DNS settings for any of your domains or if you maintain your own DNS outside of our servers, you must read this and take action. If you have not customized your DNS in any way or don’t know what this means, you do not need to do anything.
We will be making some significant changes to how we configure our email servers in the next couple of weeks, and it is very important that your DNS is configured correctly. The best way to know if your DNS is configured correctly is to query the DreamHost DNS servers directly. You can do that with the UNIX ‘host’ command with syntax similar to this:
host -t any example.com ns1.dreamhost.com
If you need assistance with this, please contact our support team as soon as possible.
If you are using the default DreamHost set up, you do not need to do anything. This is only applicable to anyone who has customized their DNS configuration in a way other than how we recommend.
Happy DreamHost DNS Team
To have lived is not enough for them, they have to talk about it. – Samuel Beckett