Email Notifications not Triggering

Many times we might have faced issue with email notifications are not triggering to a particular User/Employee. To resolve these type of issues we can follow below setup.

Scenario 1:
User Category : Default
User Name      : Abcd_Company
First Name      : Abcd
Last Name       : Company
Email              : abcd@company.com
Role                : No role assigned
If the user is created as above then he/she will not receive any email notifications, to avoid these kind of issues we need to change setup as below

Scenario 2:
User Category : Default
User Name      : 12345
First Name      : Abcd
Last Name      : Company
Email             : abcd@company.com
Role               : Employee Role(ORA_PER_EMPLOYEE_ABSTRACT)
By changing user name to Numeric and assigning an employee role we can see email notifications to user.