Error 405

I am new to this - please be patient.
I'm using a perl script - f2m.cgi
Can be viewed at URL
This program is a <FORM> mailer, that is cross platform. Meaning it is NOT dependent on sendmail or any other program. It does require a version of Perl with the standard Socket module (Perl 5.x should have this.) Also unlike other form mailers, this program actually mails the <FORM>, so all of the layout is identical to the HTML <FORM>. For this to work properly, you must be using an HTML compliant email client.
The error I'm getting is:
HTTP Error 405
405 Method Not Allowed
The method specified in the Request Line is not allowed for the resource identified by the request. Please ensure that you have the proper MIME type set up for the resource you are requesting.
Please contact the server's administrator if this problem persists.
The site is hosted on an NT Server - where do I start to try and sort this out?
Is it to do with Net::SMTP?