1.
Shades guess of outlook not being registered as the default mail client might be a good guess as to why the "Default mail client" option might not be working.
2.
If you use the 64-bit version of ScreenShot Captor
SC only exists as a 32-bit version.
3.
The reason the last option method you are trying to use of "Use a 3rd party commandline email program" might be that SC doesn't by default install sendEmail.exe
You'll find instructions on how to download it and where to put it in your ScreenshotCaptor\Tools\sendEmail\ directory
(the readme tells you to download from
http://caspian.dotco.../Software/SendEmail/ and then put it in that directory).
4.
I'm not sure why the direct SMTP wouldn't be working, though i know sometimes smtp configurations can be tricky getting the port right, etc.