ClamAV is an open source antivirus program designed for Unix and Unix-like systems. At DreamHost, this software is already installed on shared mail servers to check for malicious content. Messages caught by the antivirus filters are discarded and logged in ClamAV logs.
You can learn more about this software at ClamAV’s site:
VPS and Dedicated users
If you have a Dedicated server, you can install your own POSTFIX, create your own MX records and use your custom installation of ClamAV. This way, you can host email directly on your local machine rather than the DreamHost shared mail servers.
This is beyond the scope of DreamHost support so if anything were to error with the configuration, support would not be able to assist at all.
You can download ClamAV at the following link: