fmSpark requires the mail.it plugin, version 3.0 or higher. The plugin is registered by fmSpark automatically (the cost of which is included in your fmSpark license fee). Technically, this registration occurs in the fmSparkUtil.fp7 file (the file for which administrative access is not granted, per license restrictions).
Upon first launching fmSpark if the plugin is not installed, the user will be presented with a dialog option to install the plugin. After installing the plugin, FileMaker needs to be quit and restarted to activate the plugin. This usually is all it takes to get the plugin running.
Occasionally you'll see a message that the file "...could not be created on this disk." This usually means you're logged in as a user who does not have Admin rights on the machine (on the machine, not the FileMaker file). Try logging out of the machine and logging back in as an admin user, just to get the plugin installed.
If you need the plugin or want to check out its documentation directly, it can be downloaded from the Dacons site, here.
Once downloaded and unzipped, place the "mail.it.fmplugin" file in the Extensions folder in the FileMaker Pro 8.5 or 9 folder in your main Applications or Program Files directory. FileMaker must be restarted, if open, to make the plugin available.
FileMaker 12 has changed its set up so the Extensions folder now has privilege restrictions on it. This also prevents the automatic installation from working, so doing the manual installation for 12 may be necessary as well.
Page URL: http://docs.proofgroup.com/fmSpark/en/1.0/Developer/FileMakerPlugins