For Reports Read ->
Oracle Report Manager User's Guide Release 12.2 Part Number E22006-10
Title: Report Delivery
Link:
https://docs.oracle.com/cd/E26401_01/doc.122/e22006/T219421T576197.htm#frm_deleng_setupFor Ntf mailer , basically you will configure Workflow Mailer's outbound. (smtp)
You will write down your mail server details.. In this case, you will write down your postfix server , user and pass..