You should be able to set "smtpd_data_restrictions = reject_unauth_pipelining" in your main.cf
This option is available in "older" postfix versions and even works with postfix 2.10.
Don't know if it is as good of a measure as the 'smtpd_forbid_unauth_pipelining' that is recommended for newer versions.
mbrinkers|2 years ago
https://www.postfix.org/smtp-smuggling.html
ToniAlfredo|2 years ago