Allow impersonation using ews

Question

I'm trying to create a program in C# which should make it able to create appointments in someone else's Outlook calendar. I have code which makes it able to create appointments in my own calendar. I searched on Google and I found I should use impersonation. So I added the line:

service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, emailAddress);

This is my code:

private void button2_Click(object sender, EventArgs e) {
try{
    ExchangeService service = new ExchangeService();
    service.UseDefaultCredentials = true;   
    service.Credentials = new WebCredentials("[email protected]", "password");
    service.AutodiscoverUrl("[email protected]", adAutoDiscoCallBack);
    service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, "[email protected]");

    Appointment appointment = new Appointment(service);
    // Set the properties on the appointment object to create the appointment.
    appointment.Subject = "Tennis lesson";
    appointment.Body = "Focus on backhand this week.";
    appointment.Start = DateTime.Now.AddDays(2);
    appointment.End = appointment.Start.AddHours(1);
    appointment.Location = "Tennis club";
    appointment.ReminderDueBy = DateTime.Now;

    // Save the appointment to your calendar.
    appointment.Save(SendInvitationsMode.SendToNone);

    // Verify that the appointment was created by using the appointment's item ID.
    Item item = Item.Bind(service, appointment.Id, new PropertySet(ItemSchema.Subject));
}
}catch (Exception ex)
        {
            MessageBox.Show(ex.Message);
        }
}

internal static bool adAutoDiscoCallBack(string redirectionUrl) {
    // The default for the validation callback is to reject the URL.
    bool result = false;

    Uri redirectionUri = new Uri(redirectionUrl);

    // Validate the contents of the redirection URL. In this simple validation
    // callback, the redirection URL is considered valid if it is using HTTPS
    // to encrypt the authentication credentials. 
    if (redirectionUri.Scheme == "https") {
        result = true;
    }

    return result;
}

The problem is that I keep getting this error ""The SMTP-address has no mailbox associated with it."

Is it because impersonation isn't allowed on the server? If so how do I allow it? I hope someone can help.

Ps: Sorry for the bad english

Answer 1

A few suggestions if this is Office365 or Exchange 2013 you first need the PrimarySMTP address of the Mailbox you wish to access eg

String MailboxToAccess = "[email protected]";

Note for some tenants the SMTP and UPN/Logon are the same but that is not always the case.

This is what user you are going to be impersonating eg

service.ImpersonatedUserId = new ImpersonatedUserId(ConnectingIdType.SmtpAddress, MailboxToAccess);

You should also add in the X-AnchorMailbox header https://learn.microsoft.com/en-us/archive/blogs/webdav_101/best-practices-ews-authentication-and-access-issues eg

service.HttpHeaders.Add("X-AnchorMailbox", MailboxToAccess);

Also when you go to save the Appointment use the FolderId class with the Mailbox overload to ensure your hitting the correct Mailbox eg

FolderId CalendarFolderId = new FolderId(WellKnownFolderName.Calendar, MailboxToAccess);
appointment.Save(CalendarFolderId,SendInvitationsMode.SendToNone);

Cheers Glen