Deliverability · Glossary

Email Warmup

Also known as: domain warmup, inbox warming

Email warmup is the process of gradually increasing email volume from a new sending domain or address to build a positive reputation with mailbox providers before you run real campaigns. A brand-new domain has no track record, so sending a high volume immediately looks like spam. Warmup ramps up slowly — and ideally generates positive engagement — so the domain earns trust and your real outreach lands in the inbox instead of spam.

How warmup works

Warmup starts with a low daily send volume from the new domain and increases it gradually over a few weeks, building a history of normal-looking, well-received email. The goal is to teach mailbox providers that the domain belongs to a legitimate sender before you scale to full campaign volume. Skipping warmup is one of the most common reasons new domains land in spam — you're effectively asking providers to trust a stranger who showed up sending hundreds of emails on day one.

Doing warmup the right way

Healthy warmup builds genuine reputation rather than faking it. The reliable approach is a gradual, patient ramp on a properly authenticated, dedicated sending domain — not artificially inflating engagement, which providers increasingly detect. Because warmup takes weeks and has to run before campaigns, it's something most teams want handled automatically by their sending platform rather than managed by hand.

Warmup is the difference between a new domain that reaches the inbox and one that's filtered from day one. It's an unglamorous, time-consuming step that quietly determines whether your entire campaign gets seen.

Email Warmup: FAQ

How long does email warmup take?

Typically a few weeks of gradually increasing volume before running full campaigns. The exact time depends on the domain and target volume, but rushing it is one of the most common reasons new domains land in spam.

Do I need to warm up a new sending domain?

Yes. A brand-new domain has no reputation, so sending high volume immediately looks like spam. Warmup gradually builds trust with mailbox providers so your real outreach reaches the inbox.

See Email Warmup in action

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