Cloud control 12G - how to you tell if an email notification was sent?

Where in Cloud Control - or in the OMS log files - can you tell if an email was sent (or was attempted)?

Email notifications were working in the past - to my knowledge nothing has changed.

I've tested email via the Test Email button.  This worked.

I've forced some errors such as bringing the database down and changing the thresholds on tablespaces.  I see the events within cloud control but I'm not getting emails.

At this point I don't know if the emails just aren't being sent or if there is a problem sending emails.   I would think that you could see emails that were sent in the console but if that isn't available then I would hope that they would show up in some OMS log file.