# postconf > Postfix configuration utility. > This command displays the values of the `main.cf` configuration parameters by default and warns about possible mistyped parameter names. It can also change the `main.cf` configuration parameter values. > More information: . - Specify the directory of the `main.cf` configuration file instead of the default configuration directory: `postconf -c {{path/to/configuration_directory}}` - Edit the `main.cf` configuration file and update parameter settings with the "name=value" pairs: `postconf -e` - Print the default parameter settings of the `main.cf` instead of the actual settings: `postconf -d` - Display parameters only from the specified class. The class can be one of builtin, service, user or all: `postconf -C {{class}}` - List available SASL plug-in types for the Postfix SMTP server. The plug-in type is selected with the `smtpd_sasl_type` configuration parameter by specifying `cyrus` or `dovecot` as the name: `postconf -a` - List the names of all supported lookup table types. Lookup tables are specified as `type:name` in configuration files where the type can be `btree`, `cdb`, `hash`, `mysql`, etc: `postconf -m`