The "Allow percent hack"option controls the rewriting of the form "user%domain" to "user@domain". This is enabled by default. This option sets the "allow_percent_hack" postfix variable.
The "Append at origin" option controls the rewriting of the form "user" to "user@$mydomain". This should not be turned off. This option sets the "append_at_myorigin" postfix variable.
The "Append dot domain" option controls the rewriting of the form "user@host" to "user@host.$mydomain". This is enabled by default. This option sets the "append_dot_mydomain" postfix variable.
The "Empty address recipient" specifies the destination for mail from < > that is undeliverable (typically, bounce notifications and other notifications). By default, such mail is sent to MAILER-DAEMON.
The "Masquerade domains" option gives an optional list of domains that must have their subdomain structure stripped off.
By default, address masquerading is disabled.
The "Masquerade exceptions" option gives an optional list of user names that are not subjected to address masquerading.
By default, address masquerading makes no exceptions.
The "Swap bangpath" option controls the rewriting of the form "site!user" to "user@site". This is necessary if your machine is connected to UUCP networks. It is enabled by default.