You should set up a postmaster alias in the aliases(5) table that directs mail to a human person. The postmaster address is required to exist, so that people can report mail delivery problems. While you're updating the aliases(5) table, be sure to direct mail for the super-user to a human person too.
/etc/aliases:
postmaster: you
root: you
Execute the command “newaliases” after changing the aliases file. Instead of /etc/aliases, your alias file may be located elsewhere. Use the command “postconf alias_maps” to find out.
The Postfix system reports problems to the postmaster alias. You may not be interested in all types of trouble reports, so this reporting mechanism is configurable. The default is to report only serious problems (resource, software) to postmaster:
Default setting:
/etc/postfix/main.cf:
notify_classes = resource, software
The meaning of the classes is as follows:
bounce
Inform the postmaster of undeliverable mail. Either send the postmaster a copy of undeliverable mail that is returned to the sender, or send a transcript of the SMTP session when Postfix rejected mail. For privacy reasons, the postmaster copy of undeliverable mail is truncated after the original message headers. This implies “2bounce” (see below). See also the luser_relay feature. The notification is sent to the address specified with the bounce_notice_recipient configuration parameter (default: postmaster).
2bounce
When Postfix is unable to return undeliverable mail to the sender, send it to the postmaster instead (without truncating the message after the primary headers). The notification is sent to the address specified with the 2bounce_notice_recipient configuration parameter (default: postmaster).
delay
Inform the postmaster of delayed mail. In this case, the postmaster receives message headers only. The notification is sent to the address specified with the delay_notice_recipient configuration parameter (default: postmaster).
policy
Inform the postmaster of client requests that were rejected because of (UCE) policy restrictions. The postmaster receives a transcript of the SMTP session. The notification is sent to the address specified with the error_notice_recipient configuration parameter (default: postmaster).
protocol
Inform the postmaster of protocol errors (client or server side) or attempts by a client to execute unimplemented commands. The postmaster receives a transcript of the SMTP session. The notification is sent to the address specified with the error_notice_recipient configuration parameter (default: postmaster).
resource
Inform the postmaster of mail not delivered due to resource problems (for example, queue file write errors). The notification is sent to the address specified with the error_notice_recipient configuration parameter (default: postmaster).
software
Inform the postmaster of mail not delivered due to software problems. The notification is sent to the address specified with the error_notice_recipient configuration parameter (default: postmaster).