[root@freebsd ~]# vi /usr/local/etc/postfix/main.cf
↓最終行に下記を記入
# Virtual configuration
virtual_alias_maps = hash:/usr/local/etc/postfix/virtual
[root@freebsd ~]# vi /usr/local/etc/postfix/virtual
↓最終行に下記を記入
example.com anything
user_name@example.com user_name
[root@freebsd ~]# postmap /usr/local/etc/postfix/virtual
[root@freebsd ~]# /usr/local/etc/rc.d/postfix restart