Updating Mandrill Settings
If for any reason it becomes necessary to change the values of the Mandrill Process, stop the UEmailTracking service and follow the directions in the Initial Setup. The Mandrill key can be changed by going to the mandrillapp.com site, logging in and selecting Settings/SMTP & API Info. Then select Delete the API key and generate a new one. Make sure that you follow the instructions in 11 through 17 of the Initial Setup instructions.
For more information on Mandrill please refer to the Mandrill Support Guide.