Mr. DNS: Free DNS and Network Diagnostic Tools for Sysadmins and Email Teams

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Mr. DNS is a free collection of DNS and network diagnostic tools built for sysadmins, email administrators, and infrastructure teams. The site has been around for years, went offline for a while, and recently relaunched with an expanded tool set. Everything runs in the browser with no account required. If you work with DNS records, mail servers, or IP reputation, there is something here you will use regularly.

Mr. DNS homepage showing DNS and network diagnostic tools

DNS Tools

The DNS lookup tool handles all common record types: A, AAAA, MX, TXT, NS, SOA, CNAME, PTR, CAA, SRV, TLSA, HTTPS, MTA-STS, and BIMI. Results include TTL, geolocation data for nameservers, and flag icons for quick visual scanning.

The DNS propagation checker queries seven global resolvers simultaneously: Cloudflare, Google, Quad9, OpenDNS, AdGuard, NextDNS, and DNS.SB. Useful when you have just made a DNS change and need to see where it has landed without waiting or querying each resolver manually.

The DNSSEC checker validates the full chain of trust: DS records, DNSKEY records, RRSIG presence, and expiry. Good for confirming a DNSSEC deployment before and after changes.

Email Tools

The email tools are where Mr. DNS gets most of its daily use. The email health checker runs a combined SPF and DMARC evaluation and returns a letter grade (A through F) for your domain. One URL, one result, easy to share with a client or manager who needs a status report.

Mr. DNS email health checker showing an A grade for generatorlabs.com

Individual checkers are also available for SPF, DMARC, and DKIM when you need to dig into a specific record. The email header analyzer parses raw RFC 2822 headers and maps the full relay chain with per-hop timing and authentication results, useful for tracing a delivery failure or diagnosing a spam classification issue.

For teams managing outbound mail infrastructure, the MTA-STS checker validates DNS records and policy files, and the BIMI checker verifies SVG logos and VMC certificates for domains using brand indicators in supported mail clients.

Blacklist Checker

The blacklist checker queries your IP or domain against 15+ major RBLs and returns results in seconds. It is a solid first step when a client reports deliverability problems or when you are onboarding a new IP range and want a quick baseline.

For teams that need ongoing coverage rather than one-off checks, blacklist monitoring from Generator Labs runs continuous checks against hundreds of data sources and sends immediate alerts when a listing is detected. The free tier covers one host with no credit card required.

SSL and Network Tools

The SSL certificate checker inspects certificate details, expiry dates, SANs, issuer chain, and key type for any domain. Useful for a quick manual check before or after a certificate renewal.

For automated tracking across many domains, certificate monitoring from Generator Labs handles the ongoing work: scheduled checks, configurable expiry alert thresholds, and multi-channel notifications before anything expires.

Other network tools include ping, traceroute, port checker, HTTP headers inspector, HTTP/2 and HTTP/3 checker, and a what is my IP tool that detects both IPv4 and IPv6 with geolocation and ASN data.

Generators

Mr. DNS includes generators for SPF records and DMARC records for teams setting up email authentication from scratch. Both walk through the options and output a ready-to-paste DNS record.

Bottom Line

Mr. DNS covers the diagnostic side of DNS and email infrastructure without requiring an account or payment. For the monitoring side, Generator Labs provides continuous blacklist monitoring and certificate monitoring with alerting, picking up where the one-shot tools leave off. Both are worth bookmarking if you manage any kind of mail or DNS infrastructure.

Generator Labs: Blacklist and Certificate Monitoring for Email and Infrastructure Teams

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Generator Labs provides infrastructure monitoring for teams that need to stay ahead of two specific problems: IP and domain blacklistings that kill email deliverability, and SSL certificates that expire without warning. Both products run in the same portal, so you manage everything in one place.

Blacklist Monitoring

Blacklist monitoring runs continuous checks of your IPv4 addresses, IPv6 addresses, and domains against hundreds of RBL and URIBL data sources. The moment a listing is detected, alerts go out through whatever channels you have configured: email, SMS, Slack, Discord, PagerDuty, or webhooks.

Coverage is the differentiator. Free one-shot tools check a handful of the major lists. Generator Labs checks well over a hundred data sources on a schedule, including 30+ premium sources on Enterprise and Ultimate plans that free tools do not cover. You get notified when something changes; you are not logging in to run a manual check.

Other features worth knowing:

Full IPv6 support. IPv4 and IPv6 addresses are both monitored across all plans. As more mail infrastructure goes dual-stack, IPv6 blacklisting is a real and growing issue that most monitoring tools still treat as secondary.

Shareable public reports. Every monitored host gets a public report URL you can hand to a client, ISP, or manager without giving anyone portal access.

REST API. Full programmatic access to monitoring data and controls, with client libraries for PHP, Node.js, and Python.

Generator Labs RBL Monitoring hosts list

Blacklist Monitoring Pricing

  • Free: 1 host, 48-hour check interval, 100+ data sources. Free forever, no credit card required.
  • Professional: $8/month for 20 hosts at 24-hour intervals.
  • Enterprise: $16/month for 50 hosts at 12-hour intervals, premium data sources, custom run times.
  • Ultimate: $0.005 per check, unlimited hosts, custom intervals, all premium sources.

The Ultimate pay-per-check plan scales cleanly for larger deployments. Running 50 hosts daily against 150 data sources works out to roughly $11/month.

Certificate Monitoring

Certificate monitoring tracks SSL/TLS certificate expirations across your domains and sends alerts before anything expires. Add your domains, set alert thresholds, and the service runs automatically from there.

Both publicly-trusted and private or internal CA certificates are supported, which matters for teams running internal infrastructure that does not go through a public CA. Certificate expiry causes outages that are entirely preventable; automated monitoring removes the spreadsheet tracking and calendar reminders that most teams fall back on.

Generator Labs Certificate Monitoring monitors list

Monitoring profiles let you define reusable alert configurations across multiple monitors. Set custom expiration alert windows (5, 15, 30, 60 days, or any combination you need), choose which failure types trigger alerts, and assign private CAs or internal monitoring agents. One profile can cover dozens of monitors.

Generator Labs Certificate Monitoring add profile dialog

Certificate Monitoring Pricing

Certificate monitoring is priced at $0.01 per host per day, with no fixed tiers. You pay for what you monitor and can add or remove domains at any time.

Who It Is For

  • Email service providers and hosting companies monitoring large IP ranges
  • IT and security teams who need immediate notification when a host gets listed
  • Organizations managing many domains who need certificate expiry visibility without manual tracking
  • Developers who want API access to monitoring data for automation or integration

Get Started

Generator Labs offers continuous blacklist monitoring and certificate monitoring with solid alert coverage and a complete API. The free tier is a real free tier. Sign up at portal.generatorlabs.com to get started, no credit card required.

Net_DNS2 v1.5.0 – Version Bump (requires >= PHP 5.4)

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I’ve released version 1.5.0 of the Net_DNS2 library.

You can add it to your project using composer:

composer require pear/net_dns2

Or you can install it through the command line PEAR installer:

pear install Net_DNS2

Version 1.5.0

  • added the AMTRELAY resource record type (RFC 8777).
  • added Net_DNS2_RR::asArray(), which returns the same values as __toString(), but as an array for easier access.
  • added Net_DNS2::closeSockets(), which lets you close all cached network sockets in the resolver object.
  • added Net_DNS2::getSockets(), which returns the local sockets cache array.
  • added date_created and date_last_used to the Net_DNS2_Socket object, to track usage stats on each socket object.
  • added the SHA256, SHA384, and GOST digest defines to Lookups.php.
  • dropped the Net_DNS2_Socket_Sockets, and switch to just using the streams code. There’s no speed difference anymore.
  • fixed a bug in Net_DNS2_Packet::compress() and Net_DNS2_Packet::expand() related to dot literals in compressed names.
  • fixed a display issue in the IPSECKEY RR when displaying hostname / domain names in the gateway field.
  • fixed a couple inconsistencies in the docs.
  • fixed a PHP 7.4 bug in Sockets.php; accessing a null value as an array throws an exception now.
  • fixed Net_DNS2_RR_DS so it will be able to support other digest definitions without any other changes.
  • the Net_DNS2_RR_NIMLOC class was incorrectly named Net_DNS2_RR_NIMLOCK.
  • Net_DNS2_PrivateKey was using the wrong member variable name for the key_format value.
  • changed all references to array() to [].
  • removed all sorts of license noise from the files.
  • updated the test cases to use PHPUnit v9+.

Net_DNS2 v1.4.4 – Bugfixes and Updates for PHP 7.2

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I’ve released version 1.4.4 of the PEAR Net_DNS2 library- this release is primarily just bug fixes.

You can install it now through the command line PEAR installer:

pear install Net_DNS2

Or, you can also add it to your project using composer:

composer require pear/net_dns2

Version 1.4.4

  • Bugfix when returning an empty bitmap-type in BitMap.php – patch from BugMaster510945.
  • Added the BIND 9 private record RR (TYPE65534) – patch from BugMaster510945.
  • Added DNSSEC algorithms 13-16 (ECDSAP256SHA256, ECDSAP384SHA384, ED25519, and ED448).
  • Added SSHFP algoritm ED25519.
  • Modified Net_DNS2::sendPacket() to use current()/next() rather than the deprecated each() (deprecated in 7.2).

Python SDK for the Generator Labs REST API

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We’re extremely excited to announce the release of the office Generator Labs Python SDK. Developers can us this simple wrapper library to integrate all the features of the Generator Labs API into their existing processes.

Installation

The Python SDK can be installed via the Python package manager:

pip install generatorlabs

Or if you prefer, you can clone the source code from the official GitHub repository.

API Access Token

To authenticate API requests, you must use the Account SID and Access Token, available from the Account -> API Access section of the Generator Labs Portal.

Example Usage

Using the Python SDK only requires a few lines of code. In this example, we’ll request a list of hosts from our account:

import generatorlabs

try:
 client = generatorlabs.Client('Your Account SID', 'Your Auth Token')

data = client.hosts.get();

except generatorlabs.GeneratorLabsException as err:
 print(err)

In this example, we’ll start a manual check process, using the real-time check features of the Generator Labs API:

import generatorlabs

try:
 client = generatorlabs.Client('Your Account SID', 'Your Auth Token')

data = client.check.start({

"host": "10.10.10.11",
 "callback": "https://your.website.com/callback.php",
 "details": 1
 });

except generatorlabs.GeneratorLabsException as err:
 print(err)

See our API Reference for a complete list of all the Python SDK features.