Weekend Learning: Troubleshooting Workflow Notification Mailer

Have you ever had to find out what is causing Workflow Notification Mailer issues in your EBS environment?  If you have not encountered these issues yet, you probably will, especially when upgrading so bookmark MOS article "Troubleshooting Notification Mailer OUTBOUND_SERVER or INBOUND_SERVER Validation Failures" from document ID 1672562.1 for many different solutions to several problems you could hit.