Hitting the primary inbox (not spam or promotions) is make-or-break for every newsletter and cold-email campaign. In Episode 4 of the LetterStack Podcast, Renga sits down with Anthony Baltodano, founder of Mission Inbox and a decade-long deliverability expert, to unpack the exact tech and tactics that keep your emails landing where they belong.

What you’ll learn:

Email Deliverability 101 – why SPF, DKIM & DMARC are the “carrier, wax-seal & security guard” of email

How to warm up domains (and why skipping it tanks reputation)

Plain-text vs HTML: balancing design with inbox placement

The hidden risks of cheap domain registrars (and why you should move DNS to Cloudflare)

Tools Tony recommends for beginners (Beehiiv + MailReach) & for scale (Mission Inbox)

Weekly health checks: simple placement tests that take 10 minutes

Real-world horror stories: platform outages, blacklists, and how to dodge them

Timestamps

00:00 – Intro & why deliverability matters
02:33 – Tony’s background: SDR → deliverability consultant → Mission Inbox
05:35 – What actually happens after you hit “send”
06:56 – SPF, DKIM, DMARC explained with a “letter & seal” analogy
11:32 – Copy, links & images: how content triggers spam filters
15:54 – Why Apple & Yahoo open emails before users do
18:45 – Domain warm-up: what it is and best tools (WarmE.io, MailReach)
23:10 – Domain reputation factors: registrar, age, blacklists
30:38 – Affordable starter stack: Beehiiv + placement testing
35:30 – Tony’s 3-step deliverability checklist for creators

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Check out MissionInbox.com to explore Tony’s deliverability infrastructure platform.