Hello,

The SMTP proxy settings, which are set during the initial configuration of App Center, are saved in the Postfix configuration file. You can follow these steps to disable the proxy settings, and allow Postfix to send e-mails directly:

1. Edit the Postfix configuration file:  /etc/postfix/main.cf
    
2. The proxy setting, or relayhost, is appended to the end of this configuration file. If a proxy/relay is not desired, simply comment this line out by prefixing the line with a hash symbol:  # relayhost = [mail.domain.com]:25 . Then, save the file
    
3. Restart postfix by running the following command as root: # /etc/init.d/postfix restart

This will then remove the proxy/relay, and Postfix will then attempt to send e-mails to the recipients directly.

Let me know if this answers your question

Thanks,

Andrew