Thanks for posting your solution Miranda!
I use IX Webhosting and have been struggling with getting a contact form plugin to work. At least 7 different plugins returned 405 error codes or were working, but not sending the email.
I decided this must be an issue at IX. I had no luck with chat support at IX – they told me the plugins were the problem. Since I decided to work with Cforms II, I followed the advice given by miranda_asch … that alone didn’t work – but it might have been part of the solution.
I called IX and finally found a solution. The tech support guy – Mike C. wrote an .ini file and placed it in my root directory. Cforms is working now.