Email Warmup

Email warmup is the practice of gradually increasing how much email you send from a new domain or IP address, so mailbox providers can build a reputation for it before you send at full volume. A brand-new sending domain has no history, and a sudden spike of thousands of messages from an unknown source is exactly what spam looks like. Ramping up slowly gives providers time to see consistent, engaged sending and trust the domain, so your mail keeps landing once you scale.

When warmup matters

Warmup applies to new sending identities and to sudden changes in volume. You warm up when you move to a new domain or subdomain, when you start sending from a dedicated IP, or when your volume is about to jump well past what a provider has seen from you before. It matters most for cold or previously unused domains. If you send through a shared pool that already has an established reputation, the pool carries much of that history for you, so the ramp you need is smaller. Either way, authentication has to be in place first, because SPF, DKIM, and DMARC are what let a provider attach reputation to your domain at all.

How a warmup ramp works

A ramp starts small and grows in steps, often doubling volume every few days while the signals stay healthy. Send to your most engaged contacts first, the people who open, click, and reply, because early positive engagement is the strongest signal you can give a new domain. Watch bounce rate, spam-complaint rate, and inbox placement at each step, and slow down if bounces or complaints climb or placement slips. Keep sending steady rather than bursty, since consistent daily volume builds reputation faster than large gaps followed by spikes. See email deliverability for the metrics to track.

What not to do

Warmup is about earning a real reputation, so anything that fakes engagement works against it. Do not warm up by sending to purchased or scraped lists, which produce bounces and spam-trap hits that damage the domain you are trying to establish. Be wary of services that “warm up” an inbox by exchanging automated opens and replies between fake accounts, because providers increasingly detect that pattern and the engagement it creates is not from your actual audience. The reputation that survives a scale-up is the one built on people who genuinely opted in and want your mail. For the failure modes to avoid, see why emails go to spam.

Warmup at Loops

Loops manages sending infrastructure and volume shaping for SaaS teams, so transactional and marketing email send from one platform with the deliverability basics handled: domain setup, authentication, bounce handling, and suppression. A clean, opted-in list and steady sending are still what make a ramp healthy. See the email deliverability guide for the full checklist.

FAQ

What is email warmup?
Gradually increasing the volume you send from a new domain or IP so mailbox providers can build a reputation for it, instead of hitting them with a large, sudden send that looks like spam.

How long does warmup take?
It varies, but a new domain typically ramps over a few weeks, growing volume in steps and only continuing while bounce and complaint rates stay low. There is no fixed number, because the signal that matters is engagement, not the calendar.

Do warmup services work?
Services that ramp volume to real, engaged recipients follow sound practice. Services that generate fake opens and replies between automated inboxes do not build a reputation that holds up, and providers increasingly detect them.

Related: Email deliverability, SPF, DKIM, DMARC.