I can tell you that Outlook for Mac isn't compatible with FileMaker's Send Mail.
For More Information see: "Send Mail" and Outlook 2011 MAC
This is one of many acknowledged bugs that can be found in the Known Bug List here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: http://www.4shared.com/file/8orL8apk/FMP_Bugs.html
(This one's not really a "bug" as FileMaker and Mac with Outlook have never been compatible, but the recent release of MS Office discontinues Entourage and this has sparked a large number of problem reports...)