Exchange Service Finditems giving 407 error - c#-4.0

Question

we need to search email from outlook.com and to achieve this we are using Exchange Web Service (EWS) but getting 407 error a the time of calling FindItem method of service.
Here is the code which we are working on -
List<SearchFilter> searchFilterCollection = new List<SearchFilter>();
searchFilterCollection.Add(new SearchFilter.ContainsSubstring(ItemSchema.Subject, "Test"));
//searchFilterCollection.Add(new SearchFilter.ContainsSubstring(ItemSchema.Body, "homecoming"));
SearchFilter searchFilter = new SearchFilter.SearchFilterCollection(LogicalOperator.Or, searchFilterCollection.ToArray());
ItemView view = new ItemView(50);
// Identify the properties to return in the result set and the additional properties that are returned for each item.
view.PropertySet = new PropertySet(BasePropertySet.IdOnly, ItemSchema.Subject, ItemSchema.DateTimeReceived);
//Order the search results by the DateTimeReceived property. The sort direction is in descending order.
view.OrderBy.Add(ItemSchema.DateTimeReceived, SortDirection.Descending);
//Set the manner by which the search filter traverses the target folder. In the following example, the search filter performs a shallow traversal. Shallow is the default option; other traversal options are Associated and SoftDeleted.
view.Traversal = ItemTraversal.Shallow;
string userEmailAddress = "username#outlook.com";
string userPassword = "OutlookPassword";
ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010);
service.Url = new Uri("https://outlook.office365.com/EWS/Exchange.asmx");
service.Credentials = new WebCredentials(userEmailAddress, userPassword);
FindItemsResults<Item> findResults = service.FindItems(WellKnownFolderName.Inbox, searchFilter, view);
Getting error at last line of code.
Can you please guide what need to be correct to resolve it?
Thank You!