Open this lesson in your favourite AI. It'll walk you through the why, explain the demo, and quiz you on the try-it list.
SPF tells receiving mail servers which IP addresses are authorized to send email on behalf of your domain, blocking spoofing at the envelope level. Without it, any server on the internet can impersonate your domain and damage your reputation.
dig TXT yourdomain.com in a terminal and locate the line starting with v=spf1 — check whether your ESP's IP range or include directive is present.include: for a second ESP in a staging subdomain's SPF record and verify the lookup count stays under 10.Use these three in order. Each builds on the one before.
In one paragraph, explain what an SPF record is and what problem it solves for email senders.
Walk me through how a receiving mail server evaluates an SPF record step by step, from connection to pass/fail verdict.
Given a company using three different ESPs plus their own SMTP server, how would you design an SPF record that stays under the 10-DNS-lookup limit?