The Client version of the plug-in is for use in FileMaker Pro. The file is a zip archive (.zip), so you will need to unzip the file once it is downloaded. The downloaded file can be found in your web browser's download folder. After the file is unzipped, you should have a folder named "SMTPit_Pro_6_2" that looks like the following.

Figure 1 Unzipped archive

The files in the folder are as follows:

CNS Plug-ins License Agreement.pdf

This is the license agreement for the plug-in.

SMTPit Pro ReadMe.rtf

This file gives more information about the plug-in, including the changelog that shows what was updated in the most recent version.

SMTPit Pro.fp7

This is a FileMaker Pro 7 - 11 database. This simply directs you back to this website for documentation and examples.

SMTPit Pro.fmp12

This is a FileMaker Pro 12 database. This simply directs you back to this website for documentation and examples.

SMTPit_Pro_OSX.fmplugin

This is the plug-in file for use on OSX. If you are on Windows, you can ignore this.

SMTPit_Pro_WIN.fmx

This is the plug-in file for use on Windows. If you are on OSX, you can ignore this.

Now you have the plug-in files, continue installing the plug-in.