Initial administrative tasks when you log on for the first time includes editing your admin account and setting up appropriate aliases so that notifications that are automatically generated are routed to your admin mailbox.
Two aliases for the admin account are created during install:
Postmaster. The postmaster address is displayed in email messages that are automatically generated from Postfix when messages cannot be sent. If users reply to that address, the message is forwarded to the admin mailbox.
Root. This address is where notification messages from the operating system are sent.