Article

Email Deliverability Guide: SPF, DKIM, Warmup and Everything That Gets You to the Inbox

Satwick Ghosh (Smartlead) · Smartlead Free Intermediate

This is the one guide that walks the full technical stack in plain language: SPF, DKIM, DMARC, domain warmup timelines, and the spam and bounce thresholds Gmail and Outlook now enforce. It is written by a cold email platform, so read the product mentions with that in mind, but the DNS and warmup fundamentals apply no matter what you send with. A good starting point if your emails are quietly landing in spam and you do not yet know why.

  • SPF, DKIM, and DMARC are three DNS records, not optional. Gmail and Outlook now reject or spam bulk senders who skip them.
  • A new sending domain needs 3 to 6 weeks of warmup before real outreach. There is no shortcut, and skipping it is the most common reason first campaigns die in spam.
  • Watch your spam complaint rate (keep it well under a fraction of a percent) and bounce rate (under 2 percent) in Google Postmaster Tools, because reputation damage is hard to undo.
Open on smartlead.ai ↗

The question it answers

  1. When does cold outreach stop scaling, and what do I move to next?

Read with it

  1. The permission slip to recruit users by hand, do things manually, and deliver 'insanely great' experiences to your first few... paulgraham.com Essay · ~15 min read Do Things That Don't Scale Paul Graham
  2. Fifty-plus recent YC founders answer the exact question every early founder asks. The pattern across their answers is the lesson. YC Startup Library Article · ~10 min read Founder FAQ: How did you get your first customer? Y Combinator (50+ founders)
  3. A step-by-step, modern YC walkthrough of identifying buyers, starting conversations, and converting them into your first... YC Startup Library Video · ~20 min How to Get Your First 10 Customers Max Kolysh (Y Combinator)
  4. The canonical explanation of why linear funnels break and self-reinforcing growth loops compound, from the team that trains... Reforge Blog Article · ~15 min read Growth Loops Are the New Funnels Brian Balfour & Reforge team
  5. Battle-tested referral advice from the person who turned Airbnb's host referral program into its biggest driver of supply... Lenny's Newsletter Article · ~20 min read Building a Referrals Program Lenny Rachitsky
  6. An Indian founder story where the early demand test was manual, cold emails and direct outreach to find the first customers... Prime Venture Partners Podcast Podcast · ~50 min How Khadim Batti Built Whatfix Into a Global SaaS Leader Prime Venture Partners
eChai Partner Brands The partnership →