Configuring SMTP banner?
MXtoobox’s SuperTool reports an issue with the SMTP Banner Check.
Normally, the EHLO banner should match the MAIL_DOMAIN which in turn is supposed to match the reverse DNS pointer (PTR record). So if my mail-receiver runs at discourse.example, then the POSTCONF_myhostname should be discourse.example.
What is the right way to configure the EHLO banner?
My first intuition was to try setting HOSTNAME in mail-receiver.yml so it would replace the original host-mail-receiver.localdomain in /etc/postfix/mail-receiver-environment.json. But this does not change /etc/hostname nor does it change myhostname in the Postfix configuration.
I’m tempted to use POSTCONF_myhostname but I fear it will have unwanted side-effects since $myhostname is used in several places and then it would not match /etc/hostname anymore.
root@host-mail-receiver:/etc/postfix# postconf | grep myhostname
lmtp_lhlo_name = $myhostname
local_transport = local:$myhostname
milter_macro_daemon_name = $myhostname
myhostname = host-mail-receiver.localdomain
myorigin = $myhostname
smtp_helo_name = $myhostname
smtpd_proxy_ehlo = $myhostname
root@host-mail-receiver:/etc/postfix# cat /etc/hostname
host-mail-receiver