Hello [NAME], As you may know setting up alerts from OMSA is limited to the execute application option. On OMSA side, there are not many configurations possible. So most of the issues are normally related to the sending email application or script. So, in fact, you don't need any iDRAC configuration to make OMSA execute the application as a reaction to the alerts. But  Have you considered setting this email alerts notification from the iDRAC. In my opinion, the iDRAC would be a better option than OMSA. As the iDRAC email configuration have more options and is less dependant of other systems. Regards.
I faced an weird situation. We have a R740 server with idrac9 (v4.32.10.00) and OMSA 9.5.0 has been installed. The OS version is RHEL 7.7 I tried to configure email notifications using execute application with local SMTP server and without idrac9 configuration (to save one switch port). I can successfully connected to [URL]  After configuration, I can tested sending an email to myself on the web server and it worked, I can also received a notification while running my shell script under OS level. But, when I unplugged one of the redundant power supply trying to simulate a scenario, the email notification didn't worked. I can found events report on the web server log and also in the /var/log/message, but there is no email events triggered and log in /var/log/maillog.  I've been used this method on our other dell servers such as R430 with idrac8 and it worked well. I just can't figure out what's the difference. Does G14 server with idrac9 changes the strategy for email notification? Does idrac9 setup is necessary for OMSA email notification?    
OMSA 9.5.0 email alert issues