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add Postfix reverse hostname rejection toggle #441

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Merged
crazy-max merged 1 commit into from
Aug 31, 2026
Merged

add Postfix reverse hostname rejection toggle #441

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4 changes: 4 additions & 0 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -158,6 +158,7 @@ linux/arm64
* `POSTFIX_DEBUG`: Enable debug (default `false`)
* `POSTFIX_MYNETWORKS`: Trusted SMTP clients that may relay outbound mail through Postfix (default `127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128`)
* `POSTFIX_MESSAGE_SIZE_LIMIT`: The maximal size in bytes of a message, including envelope information (default `26214400`)
* `POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME`: Reject clients when their IP address has no reverse DNS entry (default `true`)
* `POSTFIX_STRIP_SENDER_HEADER`: Strip the Sender header from incoming emails to prevent SES rejection issues (default `false`)
* `POSTFIX_SMTPD_TLS`: Enabling TLS in the Postfix SMTP server (default `false`, possible values: `true`|`may`|`encrypt`|`ask`|`require`, see [Postfix TLS README](https://www.postfix.org/TLS_README.html#client_tls_levels))
* `POSTFIX_SMTPD_TLS_CERT_FILE`: File with the Postfix SMTP server RSA certificate in PEM format
Expand All @@ -182,6 +183,9 @@ linux/arm64
> unless every client in those ranges is trusted to relay mail. Docker port
> publishing and proxies can make external SMTP clients appear as private bridge
> addresses.
> If Docker or a proxy makes public SMTP clients appear as a local bridge address
> without reverse DNS, set `POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME=false`
> instead of trusting that bridge range.

### RSPAMD

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1 change: 1 addition & 0 deletions rootfs/etc/cont-init.d/00-env
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Expand Up @@ -86,6 +86,7 @@ POSTFIX_DEBUG=${POSTFIX_DEBUG:-false}
POSTFIX_LOG_PATH=/data/postfix/mail.log
POSTFIX_MYNETWORKS="${POSTFIX_MYNETWORKS:-127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128}"
POSTFIX_MESSAGE_SIZE_LIMIT=${POSTFIX_MESSAGE_SIZE_LIMIT:-26214400}
POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME=${POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME:-true}
POSTFIX_STRIP_SENDER_HEADER=${POSTFIX_STRIP_SENDER_HEADER:-false}
POSTFIX_SMTPD_TLS=${POSTFIX_SMTPD_TLS:-false}
POSTFIX_SMTP_TLS=${POSTFIX_SMTP_TLS:-false}
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9 changes: 7 additions & 2 deletions rootfs/etc/cont-init.d/15-config-postfix.sh
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Expand Up @@ -48,6 +48,12 @@ else
ZEN_DOMAIN="${POSTFIX_SPAMHAUS_DQS_KEY}.zen.dq.spamhaus.net"
fi

POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME_RESTRICTION=""
if [ "$POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME" = "true" ]; then
POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME_RESTRICTION=$',
reject_unknown_reverse_client_hostname'
fi

cat >>/etc/postfix/main.cf <<EOL
myhostname = ${ANONADDY_HOSTNAME}
mydomain = ${ANONADDY_DOMAIN}
Expand Down Expand Up @@ -90,8 +96,7 @@ smtpd_sender_restrictions =
permit_mynetworks,
permit_sasl_authenticated,
reject_non_fqdn_sender,
reject_unknown_sender_domain,
reject_unknown_reverse_client_hostname
reject_unknown_sender_domain${POSTFIX_REJECT_UNKNOWN_REVERSE_CLIENT_HOSTNAME_RESTRICTION}

smtpd_recipient_restrictions =
permit_mynetworks,
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