If you want to run your Postfix config in Plesk on an alternative port and still have authenticated SMTP as a possibility, you need to make a small change to the Postfix config.
The KB to add an extra SMTP port to Postfix says to add the following in your Postfix’s master.cf file.
<IP_Address>:
inet n -- -- – – smtpd -o smtpd_proxy_filter=127.0.0.1:10025
That won’t be enough for authenticated SMTP, as it doesn’t run chrooted like that. If you want to add that, change the line to this:
<IP_Address>:
inet n – n -- – smtpd -o smtpd_proxy_filter=127.0.0.1:10025
That way, your logs won’t fill up with:
warning: SASL authentication failure: cannot connect to saslauthd server: No such file or directory
warning: unknown[193.239.211.227]: SASL login authentication failed: generic failure
The solution has also been suggested to the KB, they may add it overtime directly.