Hello MWD,

The very first thing we recommend do a backup of your current installation.  To migrate and upgrade you will need to install the current version you are running, 11.x, on the new server.  Once you have everything migrated over, go through SmarterMail and make sure everything is working correctly.  To do the migration you'll actually need to follow the steps in this knowledge base article: Migrate SmarterMail to a Different Server - 16.x and older.

To upgrade to the latest build of SmarterMail, you'll need to first ensure your license key has current Maintenance and Support on it.  You will then backup your installation, do the upgrade from 11.x to 15.x, make sure SmarterMail is working correctly after your upgrade, do a backup of 15.x, then upgrade from 15.x to the latest build.  For each upgrade, please follow the instructions in Major Upgrade of SmarterMail kb article you linked.

You can get an .exe file of 11.x and 15.x when you login to your account on our web site here, https://www.smartertools.com/account#/downloads.