The SMTP gateway is not set up correctly:

Failed to send email to my.admin@myco.com: For email notifications to be sent, your Super Administrator must configure an Outgoing Mail (SMTP) Server within Enterprise Manager. (SYSMAN, myrule)

Invalid host name:

Failed to connect to gateway: badhost.oracle.com: Sending failed;
nested exception is:
javax.mail.MessagingException: Unknown SMTP 	host: badhost.example.com;

Invalid email address:

Failed to connect to gateway: rgmemeasmtp.mycorp.com: Sending failed;
nested exception is:
javax.mail.MessagingException: 550 5.7.1 	<smpemailtest_ie@example.com>... Access denied

Always use the Test button to make sure the email gateway configuration is valid. Check that an email is received at the sender's email address