Stop the mail services on the old mail server.
On the old server backup the following:
<drive>:\Program Files\SmarterTools\SmarterMail\Service\*.xml (config files)
<drive>:\SmarterMail (location of domains, logs, spool folders, etc.)
Copy these to the new server that has the same version of Smartermail installed. if there is a change in drive letters <paths>, IP addresses, etc, be sure and make these changes in your config files.
Start mail services of new server.
Here are the intructions from the Knowledge base http://www.smartertools.com/Portal/KB/a19/how-to-movingmigrating-smartermail-to-another-server.aspx?KBSearchID=143148
Mike