grep -vE '^\s*#' /path/to/the/file | sed '/^\s*$/d'

This step-by-step article shows how to set up Postfix to use an external SMTP, forward emails, and add TLS encryption to the emails.

Install packages

dnf install cyrus-sasl-plain esmtp-local-delivery s-nail

Edit /etc/esmtprc and add the following line

hostname smtp.example.com:587