The Email Deliverability Checklist We Run Before Any Campaign

The subject line gets the credit, but deliverability decides whether that subject line is ever seen at all. Before we design a single template or schedule a single send, we run the same 25-point audit on every new client account. It takes about a week. It routinely uncovers issues three previous agencies missed.

Here is the checklist, section by section, with notes on why each item matters and what tools we use to verify it.

1. Sender authentication

Mailbox providers decide trust in milliseconds based on three records. If any of them is missing, broken or unaligned, everything else on this list is playing from behind.

• Verify SPF on every domain that sends (and every alias). A failed SPF check is the single most common first-weeks problem we see.
• Confirm DKIM key length and selector. We look for 1024-bit keys people claimed to rotate but never did, and selectors that stopped resolving after an ESP migration.
• Publish a real DMARC record — not a parking-lot policy. Start at p=none, watch aggregate reports for two weeks, then escalate toward quarantine and reject.
• Check strict alignment. Return-path and From must share a domain. Alignment solves a surprising share of "it works in tests but not in production" cases.
• Add BIMI where your logo vectors and trust mark are ready. It is free sender identification and it moves brand squares into the inbox grid.

2. Reputation and blacklists

Reputation is scored per IP and per domain, and blacklists react faster than they forgive. We take a snapshot before changing anything.

• Check the sending IP and domain against the major blacklists and DNSBL aggregators — not just one lookup tool.
• Pull Google Postmaster and Microsoft Sender Data for complaint rate, spam rate and domain reputation history.
• Review bounce type distribution: a single malformed address does not hurt you, but pattern bounces (missing @, role accounts at scale) signal a bad list.
• Confirm the domain is not newly registered or about to expire — both push providers into a stricter posture.

3. List health and consent

A decaying list drags every send down. We score it before we clean it.

• Measure hard bounce rate and spam complaint rate against industry benchmarks (under 2% and under 0.1% respectively).
• Detect spam traps: old addresses, honeypots and deactivated domains purchased or scraped into the list.
• Score engagement — opens and clicks over the last 12 weeks — so cold segments are re-engaged or quarantined, not mailed blindly.
• Confirm consent is documented: where the address came from, when, and what was promised. Double opt-in is the ceiling, single opt-in has to at least be provable.

4. Sending path and content

Structure and content are where careful senders lose to sloppy filters after authentication passes.

• Consistent From identity. Same name + same domain on every message. Flip-flopping between "sales@" and "news@" resets the reputation the From domain built.
• One-click unsubscribe present and actually honored within the tools. Compliance is a deliverability feature.
• Plain-text parity. Heavy HTML-only sends with no plain-text alternative get scored harder by conservative filters.
• Subject-line hygiene: minimal punctuation stacking, no "RE:" or "FW:" fabrication, caps limited to real emphasis, and no free-money language that maps to the spam-trigger dictionary.
• Image-to-text ratio and link reputation. Long image walls with one link to a newly registered domain read like a phishing template.

We have never finished a week-one audit without finding at least five issues worth fixing immediately. The record is thirty-nine.

5. Inbox placement testing

Finally, we measure where the mail physically lands at seed addresses across Gmail, Outlook and Apple Mail. Tests are the ground truth the blacklists can only approximate.

• Seed lists must include the mailbox providers your actual recipients use — not the ones easiest to test against.
• Repeat tests at consistent cadence so placement is a trend, not a single flaky snapshot.
• Compare promotions-tab placement separately from spam; both are "delivered," but only one pays your bills.

Where to start on your own sending

If you only have one afternoon, do this: validate SPF and DKIM with a free mail-tester panel, publish a real DMARC record at p=none, quarantine every subscriber who has not engaged in three months, and read your last two weeks of bounces for patterns. That afternoon routinely produces the fastest placement gains of any email work you can do.

Or skip the learning curve and request our free deliverability audit. We run this exact checklist and send you the prioritized results, whether or not you hire us.