Free Bulk SPF & DMARC Domain Checker

Check email-related DNS records across domain lists with a free, configurable desktop utility. Bulk SPF & DMARC Domain Checker reads text-based input files, checks MX and TXT records, and saves domains that meet your selected checking conditions.

The tool is designed for administrators, developers, and technical users who need a local workflow for reviewing domain email policies. The Go source code is included with the download.

What Does the Tool Do?

The application extracts domains from supported input formats, performs an initial MX lookup, and checks SPF records on the domain and DMARC records at _dmarc.example.com. Checking conditions are controlled through a configuration file.

For example, you can configure the tool to look for +all in SPF records or p=none in DMARC records. Matching domains are collected in plain-text result files for further review.

Key Features

• Bulk domain processing: Work with multiple text files containing domains or supported email-address entries.
• SPF and DMARC checks: Check published DNS TXT records using configurable selection criteria.
• Independent checking options: Enable SPF checks, DMARC checks, or both.
• MX lookup: Check for mail-routing records before evaluating SPF and DMARC.
• Configurable concurrency: Adjust file-processing and record-processing settings to suit your machine and DNS environment.
• Custom DNS settings: Use the system resolver or configure DNS servers and fallback attempts.
• Domain exclusions: Maintain a blacklist of domains to exclude from processing.
• Domain caching and duplicate handling: Reduce repeated work when input lists contain recurring domains.
• Plain-text output: Save matching domains in TXT files that are easy to review, import, or use in another workflow.
• File-processing markers: Completed input files receive markers so they can be skipped during subsequent runs.

Go Source Code Included

The download includes the Go source code alongside the tool. This provides visibility into the parsing, DNS queries, filtering logic, configuration handling, and result-writing process. Developers can inspect the implementation and use it as a starting point for their own development work.

A Go development environment is required if you want to build the application from source.

Getting Started

1. Extract the downloaded package.
2. Prepare your input lists as plain-text files.
3. Edit settings.ini to configure input and output directories, checking conditions, concurrency, and DNS options.
4. Review the domain exclusion list before processing.
5. Run the application and review the generated TXT results.

Local Operation

Processing takes place on your computer. You do not need to upload your input files to an online analysis service. Domain names are sent to DNS resolvers as part of the normal lookup process.

Important Notes

This is a DNS-based filtering utility, not a complete email authentication or deliverability validator. It does not send test messages, verify individual mailboxes, evaluate DKIM signatures, or perform full message-level SPF and DMARC authentication.

A matching result means that a domain meets the tool's checking conditions; it does not automatically mean that the domain is secure, insecure, or suitable for sending email. DNS availability, record formatting, and configuration can affect results. Verify findings before making operational decisions.

Free to download, with Go source code included.