## `0x80070490` i.e. `ERROR_NOT_FOUND`

### Possible causes:
- The `HxTsr.exe` is unable to connect to `ess.windowsphone.net` (package: `microsoft.windowscommunicationsapps`)
- It is likely that the connection to the requested domain is blocked.
  (It's possible that a `NXDOMAIN` DNS response can result in `ERROR_NOT_FOUND`).
    
### Description:
- This error code is most likely received right after the process of adding a new account to sync,
  in the Email & accounts or the People app.
    
### Solution:
- Whitelist the `ess.windowsphone.net` domain and/or `HxTsr.exe` process
- Make sure that the `microsoft.windowscommunicationsapps` is able to successfully communicate
  with the requested domain.
      
What is the purpose of `ess.windowsphone.net`?  This undocumented domain is used to return endpoints
for 3rd party services.  For example:
```
GET https://ess.windowsphone.net/configure_email?ver=07&email=username@yahoo.com
```
      
```xml
<?xml version="1.0" encoding="UTF-8"?>
<isp-collection>
  <isp domain="yahoo.com" disp-name="yahoo.com" transport="1" in-serv="imap.mail.yahoo.com" in-uname-fmt="2" in-port="993" in-ssl="1" out-serv="smtp.mail.yahoo.com" out-auth="1" out-uname-fmt="2" out-port="465" out-ssl="1" />
</isp-collection>
```

## `0x80190001` (i.e. `HTTP_E_STATUS_UNEXPECTED` or `ERROR_INVALID_FUNCTION`)

### Possible causes:
- The `wwahost.exe` is unable to connect to `login.live.com`
- Note: If a proxy to `localhost` or `127.0.0.1` is being used on the system,
  all store or UWP apps (formerly known as Metro apps) will refuse to connect.
    
### Description:
- The most common causes are either the connections made from the UWP apps (such as Settings)
are blocked by a firewall, or they're being failed (e.g. the internet connection is unavailable).
    
### Solution:
- Whitelist the `login.live.com` domain and/or `wwahost.exe` process
- If a proxy to `localhost` or `127.0.0.1` is being used, try an app such as [**Fiddler**](https://telerik-fiddler.s3.amazonaws.com/fiddler/FiddlerSetup.exe)
  to disable the AppContainer isolation technology present in Windows 8 and later versions:  
  Click on <kbd>WinConfig</kbd> » **Exempt All** » Save Changes