checkdmarc

A Python module and command line utility for validating SPF and DMARC DNS records

usage: checkdmarc  [-h] [-p] [--ns NS [NS ...]] [--mx MX [MX ...]] [-d]
                   [-f FORMAT] [-o OUTPUT [OUTPUT ...]]
                   [-n NAMESERVER [NAMESERVER ...]] [-t TIMEOUT] [-v]
                   [-w WAIT] [--skip-tls] [--debug]
                   domain [domain ...]

 Validates and parses SPF amd DMARC DNS records

 positional arguments:
   domain                one or more domains, or a single path to a file
                         containing a list of domains

 optional arguments:
   -h, --help            show this help message and exit
   -p, --parked          indicate that the domains are parked
   --ns NS [NS ...]      approved nameserver substrings
   --mx MX [MX ...]      approved MX hostname substrings
   -d, --descriptions    include descriptions of DMARC tags in the JSON output
   -f FORMAT, --format FORMAT
                         specify JSON or CSV screen output format
   -o OUTPUT [OUTPUT ...], --output OUTPUT [OUTPUT ...]
                         one or more file paths to output to (must end in .json
                         or .csv) (silences screen output)
   -n NAMESERVER [NAMESERVER ...], --nameserver NAMESERVER [NAMESERVER ...]
                         nameservers to query (Default is Cloudflare's
   -t TIMEOUT, --timeout TIMEOUT
                         number of seconds to wait for an answer from DNS
                         (default 2.0)
   -v, --version         show program's version number and exit
   -w WAIT, --wait WAIT  number of seconds to wait between checking domains
                         (default 0.0)
   --skip-tls            skip TLS/SSL testing
   --debug               enable debugging output

Warning

It is strongly recommended to not use the --nameserver/-n setting. By default, checkdmarc uses Cloudflare's public resolvers, which are much faster and more reliable than Google, Cisco OpenDNS, or even most local resolvers.

The --nameservers/-n option should only be used if your network blocks DNS requests to outside resolvers.

$ checkdmarc fbi.gov

{
  "domain": "fbi.gov",
  "base_domain": "fbi.gov",
  "dnssec": true,
  "ns": {
    "hostnames": [
      "a1.fbi.gov",
      "a2.fbi.gov",
      "a3.fbi.gov"
    ],
    "warnings": []
  },
  "mx": {
    "hosts": [
      {
        "preference": 10,
        "hostname": "mx-east.fbi.gov",
        "addresses": [
          "153.31.160.5"
        ],
        "tls": true,
        "starttls": true
      }
    ],
    "warnings": []
  },
  "spf": {
    "record": "v=spf1 +mx ip4:153.31.0.0/16 -all",
    "valid": true,
    "dns_lookups": 1,
    "warnings": [],
    "parsed": {
      "pass": [
        {
          "value": "mx-east.fbi.gov",
          "mechanism": "mx"
        },
        {
          "value": "153.31.0.0/16",
          "mechanism": "ip4"
        }
      ],
      "neutral": [],
      "softfail": [],
      "fail": [],
      "include": [],
      "redirect": null,
      "exp": null,
      "all": "fail"
    }
  },
  "dmarc": {
    "record": "v=DMARC1; p=reject; rua=mailto:dmarc-feedback@fbi.gov,mailto:reports@dmarc.cyber.dhs.gov; ruf=mailto:dmarc-feedback@fbi.gov; pct=100",
    "valid": true,
    "location": "fbi.gov",
    "warnings": [],
    "tags": {
      "v": {
        "value": "DMARC1",
        "explicit": true
      },
      "p": {
        "value": "reject",
        "explicit": true
      },
      "rua": {
        "value": [
          {
            "scheme": "mailto",
            "address": "dmarc-feedback@fbi.gov",
            "size_limit": null
          },
          {
            "scheme": "mailto",
            "address": "reports@dmarc.cyber.dhs.gov",
            "size_limit": null
          }
        ],
        "explicit": true
      },
      "ruf": {
        "value": [
          {
            "scheme": "mailto",
            "address": "dmarc-feedback@fbi.gov",
            "size_limit": null
          }
        ],
        "explicit": true
      },
      "pct": {
        "value": 100,
        "explicit": true
      },
      "adkim": {
        "value": "r",
        "explicit": false
      },
      "aspf": {
        "value": "r",
        "explicit": false
      },
      "fo": {
        "value": [
          "0"
        ],
        "explicit": false
      },
      "rf": {
        "value": [
          "afrf"
        ],
        "explicit": false
      },
      "ri": {
        "value": 86400,
        "explicit": false
      },
      "sp": {
        "value": "reject",
        "explicit": false
      }
    }
  }
}

Installation

checkdmarc requires Python 3.

On Debian or Ubuntu systems, run:

$ sudo apt-get install python3-pip

Python 3 installers for Windows and macOS can be found at https://www.python.org/downloads/

To install or upgrade to the latest stable release of checkdmarc on macOS or Linux, run

$ sudo -H pip3 install -U checkdmarc

Or, install the latest development release directly from GitHub:

$ sudo -H pip3 install -U git+https://github.com/domainaware/checkdmarc.git

Note

On Windows, pip3 is pip, even with Python 3. So on Windows, simply substitute pip as an administrator in place of sudo pip3, in the above commands.

Documentation

https://domainaware.github.io/checkdmarc

Bug reports

Please report bugs on the GitHub issue tracker

https://github.com/domainaware/checkdmarc/issues

Resources

DMARC guides

• Demystifying DMARC - A complete guide to SPF, DKIM, and DMARC