Hi! My name is Travis and I am the creator of BlueMamba.
The form needs to be submitted to where you have webmail residing. On our setup we use an alias for webmail. Point the alias to the BlueMamba's "source/" directory. This is to keep the config and include files from being public. Add a similar line into your Apache config.
Alias /webmail /path/to/webmail/source
Your form should point to:
The alternative to this is to publicly link to the source directory. In that case your form should point to:
Here's a rough install outline I posted a while ago.
I am currently working on the next version, which will get away from the current directory structure. Its confusing to many people. Also the new version will have configurations for this form link per each theme.
Please feel free to email support at bluemamba for any comments or questions.