I think you want to use All instead of Any:
dd.Destination.Client.All(c => c.Email != "[email protected]")
                  eglasius
                   2009-03-21 09:01:32
                
              I think you want to use All instead of Any:
dd.Destination.Client.All(c => c.Email != "[email protected]")
Try
var destinations = db.DestinationDetails.
    Where(dd => dd.Language.Lang == "en-US" &&
        !dd.Destination.Client.Any(c => c.Email == "[email protected]"));