No subject line survives the spam folder. Before copy, before targeting, before any clever sequence, a cold email motion lives or dies on deliverability, and deliverability is a checklist, not an art. Here is the one we run before a single real email leaves any client's system.
Authentication: the non-negotiables
- SPF record published on every sending domain, listing exactly who may send for it.
- DKIM signing enabled, so every message carries a cryptographic proof of origin.
- DMARC policy in place. Start at monitoring, move to quarantine once reports are clean.
- Custom tracking domain, so your links carry your reputation instead of a shared one.
Since the big mailbox providers tightened bulk-sender rules, these are not best practice, they are the entry fee. A missing DMARC record in 2026 is a placement penalty you pay on every send.
Infrastructure: separate and warm
- Secondary domains for all cold sending, redirecting to the main site. The primary domain never sends cold.
- Two to three inboxes per domain, 20 to 40 cold sends per inbox per day, as covered in the volume guide.
- Two to three weeks of warmup before real sending, and warmup stays on afterwards at low level.
List hygiene: bounces are reputation damage
- Every address verified before it enters a sequence. Target under a 2% bounce rate; treat over 5% as an emergency stop.
- Catch-all addresses separated and sent carefully or not at all.
- Old lists re-verified before reuse. People change jobs, addresses die, and last quarter's clean list is this quarter's bounce farm.
Every bounce tells the provider you do not know who you are emailing. Enough of them and the provider stops caring what you wrote.
Sending behaviour and monitoring
- Human-like sending windows and randomised intervals, not a thousand messages at 9:00 sharp.
- Plain, personal formatting. Heavy HTML, images and attachments belong in newsletters, not cold email.
- Placement tests run weekly, seeding sends across real mailboxes to see where they land.
- Bounce, reply and complaint rates watched per inbox, because one burned inbox can drag a domain down with it.
- Postmaster tools checked for domain reputation, so decay is caught while it is still reversible.
The habit that makes it stick
Deliverability is not a setup task, it is an operating discipline. Everything above decays: lists age, inboxes accumulate history, providers move the line. The teams that stay in the inbox are the ones with someone watching the numbers weekly and acting on drift early. That discipline is built into everything we send inside Outbound & Pipeline, which is why our campaigns keep working in month six. If your replies vanished and you have not run a placement test, start there, or book a call and we will run the whole checklist against your setup.
