Just wanted to add this worked for me on Windows8 64bit,
BUT after downloading and running the program i then had to do the following:
go into control panel
go into programs
go into "default programs"
click on "Associate a file type or protocol with a program"
scroll way to the bottom and look for "MAILTO"
click on it and now "Pegasus Mail WSENDTO Utility" will be there
select it and you should be good.