The short answer: 2–4 weeks before meaningful volume, 3–6 weeks before a new domain carries real cold outreach. Anyone selling you a faster number is selling you a domain you’ll be replacing by fall.

The longer answer is more useful, because warmup isn’t a waiting period — it’s a specific sequence of things receivers need to observe before they trust you.

Why new domains start in the penalty box

Mailbox providers score senders on history: volume patterns, engagement, complaints, bounces. A new domain has no history, and spammers burn through fresh domains daily — so “no history” itself reads as risk. A brand-new domain that sends 500 emails on day three doesn’t look ambitious to Gmail. It looks like every spam operation Gmail has ever throttled, because that’s exactly what they look like.

(Receivers can see your domain’s age, and so can you — run any domain through our WHOIS & Domain Age tool and the registration date is right there. Ours says eleven days, but we’re doing something about it.)

Day zero: authentication before volume

Nothing below matters if authentication isn’t in place first. Since the Google/Yahoo rules of 2024 and Microsoft’s 2025 follow-up, SPF, DKIM and DMARC stopped being best practices and became the entry fee — unauthenticated mail from an unknown domain doesn’t get a warmup arc, it gets a junk folder.

Before the first send, confirm in one pass with the free Domain Health Checker:

SPF covering your actual sender
DKIM at 2048 bits, aligned to your domain
DMARC at p=none with reporting on

The ramp itself

The shape that works, roughly:

Week 1 — 5–10 emails/day, to people who will actually engage: teammates, friendly contacts, your own accounts on other providers. Replies in week one are worth more than any volume.
Week 2 — 15–25/day, first careful cold sends mixed in, targeting tight enough that replies stay plausible.
Week 3 — 30–50/day, watching bounces and spam-folder placement like a hawk.
Week 4 and on — grow ~20–30% per step, never doubling overnight, until you reach your target — which for a cold outreach mailbox should stay in the dozens per day, not hundreds.

Don’t hand-build the spreadsheet: our free Email Warmup Calculator generates the day-by-day schedule from your start date and target volume, with the safety warnings built in.

Two rules that override the schedule:

Bounces above ~2% → stop and clean the list. Every bounce tells the receiver you don’t know who you’re mailing — the worst possible signal from a domain with no credit.
Consistency beats totals. 20/day every day builds more trust than 100 every Friday. Reputation models love a steady heartbeat.

What about warmup networks?

Automated warmup pools — mailboxes that open, reply to, and rescue each other’s mail — remain genuinely useful for generating early positive signals, and remain genuinely against Google’s bulk-sender guidance when faked at scale. The honest position: a modest pool helps a new mailbox look alive; no pool substitutes for real recipients actually replying. Treat it as scaffolding, not the building.

The shortcuts that burn domains

Sending cold from your primary company domain (the one your invoices and support run on). Use a separate-but-related domain; reputation damage on the main domain is a company-wide incident.
Buying “aged” domains with unknown history — you might inherit a blocklist entry. (Check before you buy.)
Skipping straight to volume because week one felt fine. Week one always feels fine; throttling arrives in week three with no memo.

Warmup is the rare deliverability task where patience is the entire skill. Set the records, follow the ramp, watch the bounces — and in a month you own an asset: a domain receivers trust, which is the only thing in cold email that compounds.