Your client does not support opening this list with Windows Explorer

Your Client Does Not Support Opening This List With Windows Explorer 01
—————————
Message from webpage
—————————
Your client does not support opening this list with Windows Explorer.
—————————
OK
—————————

Multiple reasons can lead to this Warning message when you try “Open with Explorer” view in SharePoint. I will mention one of them I recently encountered and is related to WebDAV over TLS/SSL.

You can have WebDAV over TLS/SSL, but is a sensitive configuration. You must meet specific requirements.
Assume the following environment: CLIENT <—–> internet <—–> REVERSE PROXY (UAG/TMG/ISA/F5 …) <—–> private network <—–> SHAREPOINT WFE.
If the client is connecting from the internet to the SharePoint site using HTTPS (HTTP over TLS/SSL), in this case, if you want “Open with Explorer” to work you MUST:

  • have the reverse proxy server (UAG/TMG/ISA/F5 …) configured to NOT perform SSL Offloading. In other words, the traffic performed between the reverse proxy server and the SharePoint farm must also use HTTPS;
  • have the SharePoint farm configured to accept HTTPS connections (IIS Web Site bindings properly configured);
  • have proper Alternate Access Mappings settings on the SharePoint farm – make sure you have added the HTTPS URL in your AAM (the HTTPS URL must appear in Internal URL and Public URL for Zone)
    Your Client Does Not Support Opening This List With Windows Explorer 02

So, to put it short:

  • Do you use HTTPS and want “Open with Explorer” to work for the external users?
    You must have: CLIENT <—–> https (http over tls/ssl): internet <—–> REVERSE PROXY (UAG/TMG/ISA/F5 …) <—–> https (http over tls/ssl): private network <—–> SHAREPOINT WFE
  • Do you use HTTP and want “Open with Explorer” to work for the external users?
    You must have: CLIENT <—–> http: internet <—–> REVERSE PROXY (UAG/TMG/ISA/F5 …) <—–> http: private network <—–> SHAREPOINT WFE