sometimes on my Mac this script will crash or cause and error if I am using a non-standard client (i.e. NOT Apple's Mail).
So to get around it, I either use the SMTP option,
or else the "MailTo:" url scheme which calls the current default client for the user.
There was an issue with mismatched versions of Outlook and FileMaker causing Windows machines causing FileMaker to crash.
FileMaker 13 was a 32 bit version and required the 32 bit version of Outlook to work even on the 64 bit version of Windows.
FileMaker 14 now has both versions so you just need to make sure that FileMaker and Outlook are running the same bit version. You can run a 32 bit version of Outlook on a 64 bit Windows 7 or 8 system.