Hey Brian,
This could be caused by the Webdav module being installed on IIS.
Please try the following.
1. Open the Internet Information Services (IIS) Manager on the SmarterMail server and highlight the SmarterMail site in the tree on the left.
2. Click on the Modules icon under the IIS section in the middle pane.
3. Highlight the WebDAV module and click Remove on the right side of the window.
If this doesn't help, please ensure you are using the correct WebDav link and authenticating with the server. You can find the Web Dav link in the user's settings.
I hope this helps.
Thanks,
Zach Sylvester
Software Developer
SmarterTools Inc.
www.smartertools.com