Upgraded Postfix and now seeing "discarding EHLO keywords: CHUNKING" in maillog
Upgraded Postfix to 3.5.8-2.el8 on RHEL 8.5 and started seeing below in /var/log/maillog:
postfix/smtpd[7575]: discarding EHLO keywords: CHUNKING
Reviewed main.cf and master.cf but can’t see any directive controlling this behaviour. However postconf | grep chunking reports:
smtpd_discard_ehlo_keywords = chunking
?!?!?
RH compiled this change in the upgraded Postfix version, so unless you expressly override the behaviour in main.cf in following way, then chunking is disabled out of the box on RH.
Had to Google and sift through various docs to derive the answer to this, which is:
Append following line to /etc/postfix/main.cf:
smtpd_discard_ehlo_keywords = ''
Reload Postfix config:
systemctl reload postfix.service
Validate chunking no longer disabled:
postconf | grep chunking
Should return no results.
HOWEVER: Be aware there is a use-case for disabling chunking