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Anyone have idea for Postfix "workaround fix" on versions prior to 3.5.x ?

For example, Ubuntu 20.04 (LTS) is on 3.4 and 'smtpd_forbid_unauth_pipelining' is not available at all.

[quote] With all Postfix versions, "smtpd_data_restrictions = reject_unauth_pipelining" will stop the published exploit. [/quote]

https://www.postfix.org/smtp-smuggling.html

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.

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