Me too ...
I too get the message "An error occured while attempting to send an email to the spam check service. Please check the reply address."
Following this thread I called the hosting company and they confirm that Safe Mode is off.
So now what?
I think (just a guess) that using my SMTP I need to validate with a password when sending through this method.
I went to setup to see about Additional E-Mail Parameters. Only the checkbox works. Nothing happens .. no additional features. I downloaded the program a week ago so if any additional files were needed I assumed they were part of the download. However .. I still checked. All of the files in the Archive zip file were already in the folder (so I did nothing).
The message "Please check the reply address" .. I see a "default email from" but none of the setup fields actually say "reply address". Am I missing a setup field somewhere perhaps?