I've been using Outlook for about 8 months now without any problem until recently.   On November 5th or 6th I started getting Delivery failure messages whenever I tried sending an email.  I don't get the notice right away, it takes 6 hours or longer. 

I have Windows 8 and use Internet Explorer 11.  If I log into my email account directly through the provider website and send emails they go through fine, it's only when I send them via Outlook that they fail.  I did apply a Windows 8.1 update around the same timeframe, did the upgrade cause this issue?

Thank you