[postfix] New entry in main.cf

NethServer Version: 7.3.1611
Module: postfix

I need to include a postfix main.cf configuration:
inet_interfaces = all
However, this configuration is lost after reconfiguring the service.
What I need: that a specific app from my network can use smtp-relay from nethserver and send an email.
Thank you

Therefore configure that app with an account allowed to send email.

Email -> SMTP Access -> Allow relay…