In order to run DavMail on OSX Mountain Lion, you will need to disable Gatekeeper temporarily.

Steps:
- Open System Preferences/Security and Privacy and choose to allow applications download from anywhere.
- Run fixQuarantineFlag.command (Double click in Finder)
- Uncompress DavMail.app.zip (Double click in Finder)
- Launch DavMail application once
- Back to System Preferences/Security and Privacy, restore original setting
- You may want to move DavMail to your Applications folder