The mapping system in parsedmarc is used to identify sending sources (organizations, services, or industries) based on their reverse DNS base domains. This makes it easier to aggregate metrics, such as calculating the total volume of emails sent by a specific service like 'Intuit Mailchimp' even if they use multiple domains.
Key Components
base_reverse_dns_map.csv: The primary mapping file. It contains three fields: base_reverse_dns, name, and type.known_unknown_base_reverse_dns.txt: A list of domains that have been identified but cannot yet be categorized into a specific organization or industry.psl_overrides.txt: A list of suffixes used to fold noisy subdomains into a single base domain (e.g., folding host01.foo.com to foo.com).
Service Type Precedence
When assigning a type in base_reverse_dns_map.csv, follow this order of precedence:
- Email Security: All email security services.
- Marketing: All marketing services.
- ISP: Telecommunications providers offering internet access.
- Web Host: Web hosting providers.
- Email Provider: Email account providers.
- SaaS: Legitimate Software as a Service platforms.
- Industry-specific: Other senders using their own domain (e.g.,
Finance, Healthcare, Retail).
Note: Do not use Excel to edit CSV files, as it may corrupt Unicode characters. Use LibreOffice Calc instead.