The virtual path '/' maps to another application, which is not allowed

Just starting to use this library I get this exception when trying to send a basic email using Asp.Net MVC 5:

Nothing fancy, Just followed the instructions on the website.
I am running my application as http://localhost/sitename. If I change my url to be http://localhost/ the email works without an issue This is the same issue as https://github.com/andrewdavey/postal/issues/65

`[ArgumentException: The virtual path '/' maps to another application, which is not allowed.]
System.Web.CachedPathData.GetVirtualPathData(VirtualPath virtualPath, Boolean permitPathsOutsideApp) +12796283
System.Web.HttpContext.GetFilePathData() +60
System.Web.HttpContext.GetRuntimeConfig() +38
System.Web.HttpRequest.get_Browser() +191
System.Web.HttpRequestWrapper.get_Browser() +18
System.Web.WebPages.BrowserHelpers.GetOverriddenBrowser(HttpContextBase httpContext, Func`2 createBrowser) +360
System.Web.WebPages.DisplayModeProvider.<.ctor>b__2(HttpContextBase context) +11
System.Web.WebPages.d__4.MoveNext() +192
System.Web.Mvc.VirtualPathProviderViewEngine.GetPath(ControllerContext controllerContext, String[] locations, String[] areaLocations, String locationsPropertyName, String name, String controllerName, String cacheKeyPrefix, Boolean useCache, String[]& searchedLocations) +856
System.Web.Mvc.VirtualPathProviderViewEngine.FindView(ControllerContext controllerContext, String viewName, String masterName, Boolean useCache) +206
System.Web.Mvc.<>c__DisplayClass6.b__4(IViewEngine e) +43
System.Web.Mvc.ViewEngineCollection.Find(Func`2 lookup, Boolean trackSearchedPaths) +174
System.Web.Mvc.ViewEngineCollection.Find(Func`2 cacheLocator, Func`2 locator) +23
Postal.EmailViewRenderer.Render(Email email, String viewName) +63
Postal.EmailService.Send(Email email) +58
UHearth.Web.Controllers.<>c__DisplayClass16.b__15() in c:\Users\Remco\Documents\Visual Studio 2013\Projects\HearthstoneTracker.com\UHearth.Web\Controllers\AccountController.cs:186`