EWS SubscribeToPullNotifications does not get new emails - vb.net

Question

I had the following code written using EWS to subscribe to Pull notifications and read new emails. It was working all fine. All of a sudden it does not read the new emails. Any ideas what could the cause be? And how to resolve it?
Imports Microsoft.Exchange.WebServices.Data
Imports System.Threading
Public Class FormTest
Dim subscription As PullSubscription
Dim service As ExchangeService
Private Sub ButtonStart_Click(sender As Object, e As EventArgs) Handles ButtonStart.Click
service = New ExchangeService
service.Credentials = New WebCredentials("myusername", "mypassword", "mydomain")
service.Url = New Uri("https://webmail.mydomain.com/EWS/exchange.asmx")
subscription = service.SubscribeToPullNotifications(New FolderId() {WellKnownFolderName.Inbox}, 1440, Nothing, EventType.NewMail)
End Sub
Private Sub ButtonPoll_Click(sender As Object, e As EventArgs) Handles ButtonPoll.Click
PollEmails()
End Sub
Private Sub PollEmails()
Dim events As GetEventsResults = subscription.GetEvents()
For Each itemEvent As ItemEvent In events.ItemEvents
Dim message As EmailMessage = EmailMessage.Bind(service, itemEvent.ItemId)
message.Load()
' Do something with 'message'
Next
End Sub
End Class
Basically when I press ButtonPoll events does not contain any new evenets, even though there has been new emails since the ButtonStart was pressed.

Answer 1

Heyo!! I am doing something very similar. Looks like you have posted this question a month and a half ago so you may have solved it by now, but I wanted to put my initial experiences up here for anyone else that may be looking. The way I am posting below is a way to get notifications without having to push a poll button. This may help! I stripped all my fancy stuff out, as it is always important to learn, but this initial part of it was the most obnoxious part to figure out.
Imports System.Net
Imports System.Net.Security
Imports Microsoft.Exchange.WebServices.Data
Imports System.Security.Cryptography.X509Certificates
Public Class MainForm
Private Sub ExecuteButton_Click(sender As System.Object, e As System.EventArgs) Handles ExecuteButton.Click
Console.Clear()
Dim exch As ExchangeService = New ExchangeService(ExchangeVersion.Exchange2010_SP2)
exch.Url = New Uri("https://" + ExchangeURLTB.Text + "/EWS/Exchange.asmx")
exch.UseDefaultCredentials = False
exch.Credentials = New System.Net.NetworkCredential(UsernameTB.Text, PasswordTB.Text, DomainTB.Text)
ServicePointManager.ServerCertificateValidationCallback = New RemoteCertificateValidationCallback(AddressOf ValidateCertificate)
Dim subscribeStreaming As StreamingSubscription = exch.SubscribeToStreamingNotifications(New FolderId() {WellKnownFolderName.Inbox}, EventType.NewMail, EventType.Created, EventType.Deleted)
Dim subscribeStreamingConnection = New StreamingSubscriptionConnection(exch, 30)
subscribeStreamingConnection.AddSubscription(subscribeStreaming)
AddHandler subscribeStreamingConnection.OnNotificationEvent, AddressOf OnNotificationEvent
AddHandler subscribeStreamingConnection.OnSubscriptionError, AddressOf OnSubscriptionError
AddHandler subscribeStreamingConnection.OnDisconnect, AddressOf OnDisconnect
subscribeStreamingConnection.Open()
Console.Write("Steaming subscription open")
End Sub
Private Sub OnNotificationEvent(sender As Object, args As NotificationEventArgs)
Dim subscription As StreamingSubscription = args.Subscription
For Each notification As NotificationEvent In args.Events
Select Case notification.EventType
Case EventType.NewMail
Console.WriteLine(vbNewLine)
Console.WriteLine("-------------Mail created:-------------")
End Select
Next
End Sub
Private Sub OnSubscriptionError(sender As Object, args As SubscriptionErrorEventArgs)
End Sub
Private Sub OnDisconnect(sender As Object, args As SubscriptionErrorEventArgs)
End Sub
Private Function ValidateCertificate(ByVal sender As Object, ByVal certificate As X509Certificate, ByVal chain As X509Chain, ByVal sslPolicyErrors As SslPolicyErrors) As Boolean
'Return True to force the certificate to be accepted.
Return True
End Function
End Class