Impersonation without a Domain Account

I have browsed the knowledge base and it seems if you want to use UNC paths to access root folders you should create a Domain Account. 

The way we are trying to use FileVista is on an internal web server managing 5 web servers root folders which are hosted by our thrid party. 

Because of this configuration I am unable to have a common domain account across these servers as they do not reside on our domain.

I have create a local user account on each of the web servers with permissions to access the web folders I want to manage. Is there a way of specifying the user account to use when configuring root folders ?

Is there any other way I can centralize the use of Filevista to manage this environment ?

Sorry for the late response.

You can also use duplicate local accounts instead of domain accounts.

First include the below settings in web.config:

<authentication mode="Windows" />
<identity impersonate="true" userName="SomeUserX" password="Password123" /> 

FileVista will be executed under the identity of SomeUserX directly. So, you need to make sure SomeUserX can access the network share. If you were connected do a domain, this would be easy because you would go to the file server machine and give permissions directly to this domain user as you  can select him in the list.
However, you can not select and add a user of another computer if there is no domain. That's why you need to create the same user with same password on the file server.
FileVista is dependant on Windows permissions so you should first try in Windows Explorer if you can access the share with the user SomeUserX that is created on both machines. If Windows can access then FileVista will be able to access too.

Let me know the results.