diff --git a/lib/redmine_dmsf/webdav/controller.rb b/lib/redmine_dmsf/webdav/controller.rb
index 9d52032c..19a33570 100644
--- a/lib/redmine_dmsf/webdav/controller.rb
+++ b/lib/redmine_dmsf/webdav/controller.rb
@@ -28,16 +28,32 @@ module RedmineDmsf
 
       # Return response to OPTIONS
       def options
-        # Always return MethodNotAllowed(405) because how MsOffice uses anonymous OPTIONS request.
-        # See https://support.microsoft.com/en-us/kb/2019105
-        MethodNotAllowed
+        # exist? returns false if user is anonymous for ProjectResource and DmsfResource, but not for IndexResource.
+        unless(resource.exist? || (User.current && User.current.anonymous?))
+          # Return NotFound if resource does not exist and the request is not anonymous.
+          NotFound
+        else
+          if request.env.has_key?('HTTP_X_OFFICE_MAJOR_VERSION') && User.current && User.current.anonymous?
+            # Anonymous request from MsOffice, respond 405.
+            # If responding with 401 then MsOffice will fail.
+            # If responding with 200 then MsOffice will think that anonymous access is ok for everything.
+            # Responding with 405 is a workaround found in https://support.microsoft.com/en-us/kb/2019105
+            MethodNotAllowed
+          else
+            resource.options
+          end
+        end
       end
 
       # Return response to HEAD
       def head
-        # Don't check resource.exist? because it returns false for anonymous requests and MsOffice's uses anonymous HEAD requests.
-        # See https://support.microsoft.com/en-us/kb/2019105
-        resource.head(request, response)
+        # exist? returns false if user is anonymous for ProjectResource and DmsfResource, but not for IndexResource.
+        unless(resource.exist? || (request.env.has_key?('HTTP_X_OFFICE_MAJOR_VERSION') && User.current && User.current.anonymous?))
+          # Return NotFound if resource does not exist and the request is not from an anonymous MsOffice product.
+          NotFound
+        else
+          resource.head(request, response)
+        end
       end
 
       # Return response to PROPFIND
diff --git a/lib/redmine_dmsf/webdav/dmsf_resource.rb b/lib/redmine_dmsf/webdav/dmsf_resource.rb
index f12dde95..befbdbc0 100644
--- a/lib/redmine_dmsf/webdav/dmsf_resource.rb
+++ b/lib/redmine_dmsf/webdav/dmsf_resource.rb
@@ -201,6 +201,7 @@ module RedmineDmsf
       ##
       def head(request, response)
         raise NotFound unless project && project.module_enabled?('dmsf') && (folder || file)
+        
         if collection?
           html_display(true)
           response['Content-Length'] = response.body.bytesize.to_s
@@ -628,6 +629,13 @@ module RedmineDmsf
         end
       end
 
+      def options_req
+        response["Allow"] = 'OPTIONS,HEAD,GET,PUT,POST,DELETE,PROPFIND,PROPPATCH,MKCOL,COPY,MOVE,LOCK,UNLOCK'
+        response["Dav"] = '1, 2'
+        response["Ms-Author-Via"] = "DAV"
+        OK
+      end
+
       private
       # Prepare file for download using Rack functionality:
       # Download (see RedmineDmsf::Webdav::Download) extends Rack::File to allow single-file
diff --git a/lib/redmine_dmsf/webdav/index_resource.rb b/lib/redmine_dmsf/webdav/index_resource.rb
index 0acf48e0..7ad71a92 100644
--- a/lib/redmine_dmsf/webdav/index_resource.rb
+++ b/lib/redmine_dmsf/webdav/index_resource.rb
@@ -80,6 +80,14 @@ module RedmineDmsf
         OK
       end
 
+      def options_req
+        response["Allow"] = 'OPTIONS,HEAD,GET,PUT,POST,DELETE,PROPFIND,PROPPATCH,MKCOL,COPY,MOVE,LOCK,UNLOCK'
+        #response["Allow"] = 'OPTIONS,PROPFIND'
+        response["Dav"] = '1, 2'
+        response["Ms-Author-Via"] = "DAV"
+        OK
+      end
+
       # Bugfix: Ensure that this level never indicates a parent
       def parent
         nil
diff --git a/lib/redmine_dmsf/webdav/project_resource.rb b/lib/redmine_dmsf/webdav/project_resource.rb
index 36a9588b..47a79df0 100644
--- a/lib/redmine_dmsf/webdav/project_resource.rb
+++ b/lib/redmine_dmsf/webdav/project_resource.rb
@@ -81,9 +81,14 @@ module RedmineDmsf
       end
 
       def head(request, response)
-        html_display(true)
-        response['Content-Length'] = response.body.bytesize.to_s
-        OK        
+        # HEAD must be allowed even for anonymous users, so just verify that the project exists and that the dmsf module is enabled.
+        if project.nil? || !project.module_enabled?('dmsf')
+          NotFound
+        else
+          html_display(true)
+          response['Content-Length'] = response.body.bytesize.to_s
+          OK        
+        end
       end
 
       def get(request, response)
@@ -92,6 +97,13 @@ module RedmineDmsf
         OK
       end
 
+      def options_req
+        response["Allow"] = 'OPTIONS,HEAD,GET,PUT,POST,DELETE,PROPFIND,PROPPATCH,MKCOL,COPY,MOVE,LOCK,UNLOCK'
+        response["Dav"] = '1, 2'
+        response["Ms-Author-Via"] = "DAV"
+        OK
+      end
+
       def folder
         nil
       end
diff --git a/lib/redmine_dmsf/webdav/resource_proxy.rb b/lib/redmine_dmsf/webdav/resource_proxy.rb
index 782ff67d..06999d0d 100644
--- a/lib/redmine_dmsf/webdav/resource_proxy.rb
+++ b/lib/redmine_dmsf/webdav/resource_proxy.rb
@@ -52,9 +52,12 @@ module RedmineDmsf
         # seems the next best step, if the request method is OPTIONS return true, controller will simply
         # call the options method within, which accesses nothing, just returns headers about dav env.
         #return true if @request.request_method.downcase == 'options' && (path == '/' || path.empty?)
-        # MsOffice does anonymous OPTIONS and HEAD requests.
+
+        # Allow anonymous OPTIONS requests.
         return true if @request.request_method.downcase == 'options'
+        # Allow anonymous HEAD requests.
         return true if @request.request_method.downcase == 'head'
+
         return false unless username && password
         User.current = User.try_to_login(username, password)
         return User.current && !User.current.anonymous?
@@ -164,6 +167,9 @@ module RedmineDmsf
         @resource_c.properties
       end
 
+      def options
+        @resource_c.options_req
+      end
     end
   end
 end