postfix error unused parameter

Okay so you are following the old how-to where they used postfix package with older version. With the version you've installed all that parameters outdated or got changed. You need to follow current postfix configuration guide.

In all those warnings Postfix, does not understand or interpret from your config. The alert is just there to tell you that expected behavior may not be as intended. So refer to man 5 postconf or review http://www.postfix.org/postconf.5.html for correct names and parameters.

smtpd_sasl_application_name (default: smtpd) The application name that the Postfix SMTP server uses for SASL server initialization. This controls the name of the SASL configuration file. The default value is smtpd, corresponding to a SASL configuration file named smtpd.conf.

This feature is available in Postfix 2.1 and 2.2. With Postfix 2.3 it was renamed to smtpd_sasl_path.

The excerpt is from man pages. So basically replace it with

smtpd_sasl_path=smtpd

This worked for me.