We can help you with this stuff. I seems like you have 2 different issues here. The best way to get help here is to make one thread for each individual issue. Since you included the specific error information here in this thread for your "Not Acceptable" issue, we can follow through with that here. For help setting up your email, feel free to open a new thread for that.
"Not Acceptable" errors are an Apache error code 406. From my experience, 406 errors most likely are due to tripping a mod_security rule. HostNed's servers run mod_security for your protection and I am very glad they do. The challenge here is to determine which rule your script is breaking. That would be very hard, but is not impossible. We can travel that path if willing later.
So can the mod_security be turned off? Yes, it can. The best way to do that is through an .htaccess override. Under your /httpdocs (or root web directory) create a file named .htaccess (if one is already there you can edit it) and include the following lines:
## Disable mod_security
Then save the file and give 'er another go.