Email Warmup in 2026: How to Warm Up a New Domain Without Landing in Spam
Send 500 cold emails from a brand-new domain and most will land in spam — not because of your copy, but because the domain has no sending history. Warmup builds that history deliberately. Here is the schedule, the prerequisites, and the mistakes that reset your progress.
What email warmup actually is
Mailbox providers score sending domains and IPs on history. A brand-new domain that suddenly sends 500 emails a day looks exactly like a spammer spinning up infrastructure — so providers throttle it into spam regardless of content quality. Warmup is the process of building sending history gradually so filters learn to trust you before you need real volume.
The warmup schedule that works
Timelines vary by provider strictness, but this progression is a reliable baseline for a new domain:
- Week 1: 10–20 emails/day to engaged recipients (colleagues, partners) who open and reply
- Week 2: 30–50/day, start mixing in real prospects with the strongest fit
- Weeks 3–4: 75–150/day, watch bounce and spam-complaint rates daily
- Weeks 5–6: scale toward target volume, adding no more than ~30% per week
- Ongoing: never jump volume more than 2× in a week, even on a warmed domain
Replies are the strongest positive signal a mailbox provider can see — early warmup emails should go to people who will actually respond, not to a purchased list.
Before warmup: the prerequisites
- Authentication first: SPF, DKIM, and DMARC must pass before the first send — our setup guide walks through all three
- Separate domain for cold outreach: send from a cousin domain (e.g. trysendburg.com) so your primary domain’s reputation is never at risk
- Verify every address before sending: bounces during warmup are disproportionately damaging — a 5% bounce rate in week two can undo everything
- Plain-text style emails: heavy HTML templates from a new domain raise filter suspicion
Automated warmup tools — and their limits
Warmup services (Instantly, Lemwarm, Mailreach and similar) exchange automated emails between member inboxes, generating opens and replies. They accelerate the early weeks, but two caveats: Google and Microsoft actively detect warmup networks, and automated engagement does not teach filters about your real audience. Use them as a supplement to genuine early sends, not a replacement.
How long until you are safe
A domain is reasonably warmed after 4–6 weeks of consistent, low-bounce sending. Reputation is never permanent though — a single bad campaign (high bounces or spam complaints) can reset months of history. That is why teams verify lists before every send, not just during warmup. You can check any list free with our free email verifier.