Guides

• SPF "too many DNS lookups" (permerror): count and fix the 10-lookup limit
  What counts toward the SPF 10 DNS lookup limit, why nested includes break it, and how to get back under it without risky flattening.
• DMARC record checker and tag reference (p, sp, pct, rua, adkim, aspf)
  Every DMARC tag explained with valid values, common mistakes, and how external rua report addresses must be authorized.
• Gmail, Yahoo and Outlook bulk sender requirements: DNS checklist
  What Gmail, Yahoo (Feb 2024) and Outlook.com (May 2025) require from senders of 5,000+ messages a day, and which parts you can check in DNS.
• How to find your DKIM selector (Google, Microsoft 365, others)
  DKIM selectors can't be listed from DNS. Where to find yours and the selectors common providers use.
• Domain expiry date lookup with RDAP (the WHOIS replacement)
  Look up a domain's registrar, creation and expiry dates through RDAP, which replaced port-43 WHOIS for gTLDs.