DNSBLOG(8)

💖 dnsblog — the Postfix DNS allow/denylist logger, bestie 💖

okay so welcome to dnsblog(8) from the System Manager's Manual, and no this is not boring, this is the little server that does DNS allow/denylist lookups for you and it's lowkey iconic 🦋

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✨ NAME ✨

dnsblog — Postfix DNS allow/denylist logger. that's it, that's the whole job description, and she does it flawlessly 💅

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✨ SYNOPSIS ✨

dnsblog [generic Postfix daemon options]

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✨ DESCRIPTION ✨

so the dnsblog(8) server implements an ad-hoc DNS allow/denylist lookup service. like, it's a whole vibe. 🎀

heads up bestie: this may eventually be replaced by an UDP client that is built directly into the postscreen(8) server. so enjoy her while she's here fr fr 😭

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✨ PROTOCOL ✨

okay so here's the tea, with each connection, the dnsblog(8) server receives a DNS allow/denylist domain name, an IP address, and an ID. 🫶

if the IP address is listed under the DNS allow/denylist, the dnsblog(8) server logs the match and replies with the query arguments plus an address list with the resulting IP addresses, separated by whitespace, and the reply TTL. slay. ✨

otherwise it replies with the query arguments plus an empty address list and the reply TTL — and the reply TTL is -1 if there is no reply, or a negative reply that contains no SOA record. 🙈

finally, the dnsblog(8) server closes the connection. bye bestie 👋

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✨ DIAGNOSTICS ✨

problems and transactions are logged to syslogd(8) or postlogd(8). she's not quiet about her feelings 💜

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✨ CONFIGURATION PARAMETERS ✨

changes to main.cf are picked up automatically, as dnsblog(8) processes run for only a limited amount of time. use the command postfix reload to speed up a change. no cap. ⚡

the text below provides only a parameter summary. see postconf(5) for more details including examples. 👑

• config_directory (see postconf -d output) — the default location of the Postfix main.cf and master.cf configuration files.
• daemon_timeout (18000s) — how much time a Postfix daemon process may take to handle a request before it is terminated by a built-in watchdog timer.
• postscreen_dnsbl_sites (empty) — optional list of patterns with DNS allow/denylist domains, filters and weight factors.
• ipc_timeout (3600s) — the time limit for sending or receiving information over an internal communication channel.
• process_id (read-only) — the process ID of a Postfix command or daemon process.
• process_name (read-only) — the process name of a Postfix command or daemon process.
• queue_directory (see postconf -d output) — the location of the Postfix top-level queue directory.
• syslog_facility (mail) — the syslog facility of Postfix logging.
• syslog_name (see postconf -d output) — a prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd".

🌈 available in Postfix 3.3 and later:

• service_name (read-only) — the master.cf service name of a Postfix daemon process.

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✨ SEE ALSO ✨

• smtpd(8), Postfix SMTP server
• postconf(5), configuration parameters
• postlogd(8), Postfix logging
• syslogd(8), system logging

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✨ LICENSE ✨

the Secure Mailer license must be distributed with this software. periodt. 💅

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✨ HISTORY ✨

this service was introduced with Postfix version 2.8. she's been serving looks since day one 👑

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✨ AUTHOR(S) ✨

Wietse Venema IBM T.J. Watson Research P.O. Box 704 Yorktown Heights, NY 10598, USA

Wietse Venema Google, Inc. 111 8th Avenue New York, NY 10011, USA

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okay that's the whole page bestie, mwah 💖 this was the dnsblog(8) page from the System Manager's Manual, and the footer said DNSBLOG(8) at the very bottom — so consider this your cute little sign-off, love u, go log some DNS matches 🦋✨🎀