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🏷️ NAME

dnsblog - Postfix DNS allow/denylist logger

🚀 Quick Reference

Use Case	Command	Description
🚀 Start daemon	dnsblog [generic Postfix daemon options]	Launch the DNS allow/denylist logger service
🔄 Reload configuration	postfix reload	Speed up pickup of configuration changes
🔍 View logs	tail -f /var/log/mail.log	Monitor syslog for dnsblog transactions and diagnostics
⚙️ Configure DNSBL sites	postconf postscreen_dnsbl_sites	Set or view the list of DNS allow/denylist domains, filters, and weight factors
🕒 Check daemon timeout	postconf daemon_timeout	View or set the time limit for handling a request (default: 18000s)

📋 Synopsis

dnsblog [generic Postfix daemon options]

📖 Description

The dnsblog(8) server implements an ad-hoc DNS allow/denylist lookup service. This may eventually be replaced by an UDP client that is built directly into the postscreen(8) server.

🔄 Protocol

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. Otherwise it replies with the query arguments plus an empty address list and the reply TTL; 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.

🩺 Diagnostics

Problems and transactions are logged to syslogd(8) or postlogd(8).

⚙️ 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.

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 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.

📚 See Also

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

📜 License

The Secure Mailer license must be distributed with this software.

🕰️ History

This service was introduced with Postfix version 2.8.

👤 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

🏷️ NAME 🚀 Quick Reference 📋 Synopsis 📖 Description 🔄 Protocol 🩺 Diagnostics ⚙️ Configuration Parameters 📚 See Also 📜 License 🕰️ History 👤 Author(s)