In order to deactivate a license and revert an installation back to the free edition, remove the license key and activation code from the mailconfig.xml by doing the following:

Applies to SmarterMail 8.x - 15.x:

Log into your server as the administrator.

Using Window Explorer, navigate to the installation folder for the SmarterMail service (by default c:\program files\smartertools\smartermail\service).

Make a backup of the file mailconfig.xml.

Open the mailconfig.xml file with Notepad.

Find and delete these lines:

<licenseKey></licenseKey>
<activation></activation>

Save the file and then close it.

Stop and Start the SmarterMail Service.