Office 365 Exchange EWS: "Access is denied. Check credentials and try again., The process failed to get the correct properties."

Question

Trying to create an appointment into a shared mailbox using the following code:

ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010);
service.Credentials = new WebCredentials("user_id", "password");
service.AutodiscoverUrl(user_id, RedirectionUrlValidationCallback); //resolves to https://outlook.office365.com/EWS/Exchange.asmx

Appointment meeting1 = new Appointment(service);
            meeting1.Subject = "subject";
            meeting1.Body = "body";
            meeting1.Start = Convert.ToDateTime("some datetime");

            DateTime end = Convert.ToDateTime("some datetime");
            meeting1.End = end.AddMinutes(Convert.ToInt32("some number"));

ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => true;

Mailbox test = new Mailbox("some email");
FolderId folderid = new FolderId(WellKnownFolderName.Calendar, test);
meeting1.Save(folderid,SendInvitationsMode.SendToAllAndSaveCopy);

The error it returns is:

    Access is denied. Check credentials and try again., The process failed to get the correct properties.

I know the credentials are correct because the call to AutodiscoverUrl returned a valid URL. So im not sure why its saying "access is denied" when calling save()?

Answer 1

Once again, answering my own question.

The particular user being passed needed to be granted write permissions to the mailbox folder in question.