Module 5: Deliverability
The best email in the world earns nothing from the spam folder. Deliverability is the unglamorous technical foundation — proving you're legitimate, keeping your list clean, and behaving like a sender inbox providers trust. Set it up once, maintain it lightly, and your emails keep landing where readers can see them.
SPF, DKIM, and DMARC in plain English
Inbox providers need proof that your email really came from you and not someone spoofing your domain. Three DNS records provide that proof, and while the acronyms sound intimidating, each one does a simple job. SPF (Sender Policy Framework) publishes a list of servers allowed to send mail for your domain — it says "these mail servers speak for me." DKIM (DomainKeys Identified Mail) attaches a cryptographic signature to each email, like a wax seal that proves the message wasn't tampered with in transit. DMARC ties them together with a policy telling receivers what to do when mail fails the checks — nothing, quarantine it, or reject it outright.
Setting them up is a one-time chore your ESP walks you through. In your ESP's settings you'll find a deliverability or domain authentication section that generates the exact DNS records you need — typically one or two TXT records for SPF and DKIM, plus a DMARC record. Copy those into your domain registrar's DNS settings (where you bought your domain), save, and wait: DNS changes can take up to 48 hours to propagate, though it's often much faster. Then go back to your ESP and hit its "verify" button until all three show as passing. Do this before you send your first campaign, not after deliverability problems appear.
Your path
SPF
Publishes the servers allowed to send for your domain — “these mail servers speak for me.”
DKIM
Attaches a cryptographic signature to each email, like a wax seal proving the message wasn’t tampered with in transit.
DMARC
Ties them together with a policy telling receivers what to do when mail fails the checks.
Build brief
What’s your current sending setup — your own domain, a free address, or nothing yet — and what’s the first technical fix you need to make?
Saved
Keeping your list clean (bounces, inactives)
Start with bounces. A hard bounce means the address doesn't exist — typo'd at signup, deactivated, fake. Your ESP removes hard bounces automatically after the first failure; let it, and never re-add them. A soft bounce means a temporary problem — full inbox, server hiccup — and one or two are nothing to worry about. But an address that soft-bounces on every send for weeks is effectively dead; most ESPs will suppress chronic soft bounces for you, but check your bounce report monthly and manually suppress any the system missed. Never, ever buy a list to "grow faster" — purchased addresses bounce, complain, and can get your domain blacklisted within a single send.
Then handle the inactives — subscribers who receive your mail but haven't opened or clicked in 6 to 12 months. (Treat open data loosely, since privacy features inflate it; clicks are the honest signal.) Don't just delete them: send one genuine win-back email first — "Hey, you haven't opened in a while — still want these? Click here to stay." Those who click stay; those who don't get removed. It feels painful to shrink your list on purpose, but a list of 800 engaged readers will outperform a list of 5,000 ghosts on every metric that matters, including revenue. Run this cleanup twice a year and put it on your calendar.
Re-engagement email — send to subscribers inactive 90+ days before you remove them:
Subject: Should I stop emailing you?
Hi [name],
You signed up for [magnet/topic] a while back, but you haven't opened lately — totally fine. I'm cleaning up my list this week.
Want to stay? Just hit reply and say hi. No reply and I'll remove you on Friday — no hard feelings.
[Your name]
Build brief
How would you honestly describe your list’s health right now — and which subscribers probably shouldn’t be on it anymore?
Saved
Staying out of the spam folder
Spam filters score your mail, and the biggest factor is engagement: do recipients open, click, and reply — or ignore and delete? Wanted mail from a consistent sender to an engaged list almost never has spam problems. Your sender reputation is earned over months and can be damaged in a weekend, so protect it like the asset it is.
Going from 50 emails a month to 50,000 overnight on a new domain — a product launch, a big import, a "we finally have a list" moment. To inbox providers that pattern looks exactly like a spammer, and your sender reputation takes the hit. New domains need a ramp: start with your most engaged segment, increase volume gradually over weeks, and let the engagement signals build. Patience here is a deliverability strategy, not just caution.
Check your three DNS records: log into your domain registrar, confirm SPF, DKIM, and DMARC are all published for your sending domain. If any are missing, your ESP's help docs have a setup guide — most take under 20 minutes and it's the single highest-leverage deliverability task.
What is the single biggest factor inbox providers use to decide if your mail reaches the inbox?