Outlook Threshold - 5MB default
Outlook LeapFILE Options
Your Outlook Threshold setting defaults to 5MB when the plugin is installed, this means any attachment of 5MB or larger will automatically be sent via LeapFILE.
If you wish to disable or increase the threshold simply click the LF Options button in your Outlook ribbon, then either disable (uncheck) the Use threshold option and make all LeapFILE transfers through Outlook completely manual - or increase the size as need to automatically send via LeapFILE when you meet or exceed the specified size limit.