Classifying Email Providers of 2000+ Swiss Municipalities via DNS

The post describes a pipeline and interactive map that classifies email hosting providers for Swiss municipalities by analyzing public DNS records, including MX, CNAME, SPF, and autodiscover data. The methodology uses a hierarchical decision tree with keyword matching, gateway detection, ASN lookups, and website scraping to categorize providers into seven groups (e.g., Microsoft, Google, Swiss ISPs). The project includes confidence scoring and multiple DNS resolvers for resilience. The author seeks feedback on methodology gaps, edge cases, and potential improvements.