Errors returned when emailing from Office 365

Hello,

I have configured my Office 365 account so that I can send outgoing emails from my nopCommerce setup.  I have also created a new Email account in nopCommerce (Configuration > Email accounts > add new) with the right SMTP server and authentication settings.  I am able to get test emails from the "Edit email account details" screen, but the System > Log has a new entry for every email with the following details:

System.Net.WebException: The remote server returned an error: (403) Forbidden.
   at System.Net.WebClient.UploadValues(Uri address, String method, NameValueCollection data)
   at System.Net.WebClient.UploadValues(String address, NameValueCollection data)
   at Nop.Services.Tasks.TaskThread.Run()

The website is also not sending any automated emails for new account validation, order receipts, etc.  All automated emails stay in the message queue.  I am a little confused because test emails are going through but automated emails are not.

Is there anything I am doing wrong in the configuration?

I am grateful for any help I can get.

Which port are you using Port 587 ?
Either way the port you are using might be blocked on the server / firewall

Yes, I am using 587.  But if the port was blocked on the firewall, shouldn't the test emails be blocked also?