The license file is loaded from the run folder of your application (AppDomain.CurrentDomain.BaseDirectory).
You can use following code to get the license path and status pragmatically:
using Limilabs.Mail.Licensing;
// ...
string fileName = LicenseHelper.GetLicensePath();
LicenseStatus status = LicenseHelper.GetLicenseStatus();
Remember also that your application needs to have read access to this file.