https://dns-lookup.com/developers
DNS Lookup API Documentation - Free DNS API | DNS Lookup | DNS Lookup
Free DNS lookup API for developers. Query DNS records, WHOIS data, SSL certificates, and more. RESTful API with JSON responses. No authentication required.
dns lookup apidocumentationfree
https://dns-lookup.whoisxmlapi.com/
DNS records lookup products for MX, NS, SPF, etc. record | WhoisXML API
Check the NS, MX, SPF, A, SOA, TXT, etc. records / DNS server info of a domain name with our API, lookup tool, and database covering 2B hostnames.
dns recordswhoisxml apilookupproductsmx