I keep getting a message saying that the plug-in SMTPit Pro is not installed?

Youmehub uses the SPTPit Pro FileMaker Plug-in technology from Comm-Unity Networking Systems for sending e-mails.

To install this plug-in copy the file named 'SMTPit_Pro_OSX.fmplugin' for Mac OSX or 'SMTPit_Pro_WIN.FMX' for Windows, which you will find in Youmehub's Plug-ins folder, into the folder named Extensions inside the FileMaker Pro application folder. You will need to do this for each user who will be accessing the database.