Benchmarks / Warmup duration

How long should you warm up an email domain before a campaign?

Based on 850 million+ emails · Smartlead platform data

The average sender warms up a new mailbox for 8 days before its first campaign, down from 9.4 days a year earlier. Published guides advise anywhere from 2 weeks to 3 months for a new domain.

Warmup benchmarks

Built from more than 850 million emails sent through Smartlead.

Measure	A year earlier	Now	Change
Days of warmup before the first campaign	9.4 days	8.0 days	1.4 days shorter (15%)
Warmup emails reaching the inbox	-	About 99% on every major provider	-

What the data shows

Senders are reaching their first campaign faster than they did a year ago. The average mailbox now warms up for 8 days before it sends, well under the 2 weeks to 3 months that published guides recommend for a new domain.

Warmup itself is not the bottleneck. Warmup emails reach the inbox about 99% of the time on Outlook, Gmail and custom servers alike. What changes at launch is volume per mailbox and the quality of the list.

What this data can't tell you

These numbers describe what senders did, not whether it worked. The data doesn't compare reply rates by warmup length, so it can't say whether 8 days is enough for a given domain. It also doesn't separate brand-new domains from aged ones.

How to use these benchmarks

Set up SPF, DKIM and DMARC before warmup starts. Verified senders need 108 contacts per reply against 120 for unverified ones.
Start sending near the typical volume. The median mailbox sends about 14 cold emails a day, and the heaviest 10% send 42.
Verify the list before the first campaign. The median sender bounces at 1.54%, and a quarter of senders bounce at 3.21% or higher.
Keep warmup running while the first campaigns ramp up. The step-by-step setup is in the email warm-up guide.
If you can't wait for warmup, pre-warmed mailboxes skip it.

Frequently asked questions

How long does it take to warm up a new email address?

The average sender warms up a new mailbox for 8 days before its first campaign, down from 9.4 days a year earlier. Published guides advise anywhere from 2 weeks to 3 months. The data shows what senders actually do, which is shorter than most advice.

Is 8 days of warmup enough?

It is what the average sender does, not a proven minimum. The data measures practice, not results by warmup length. Watch inbox placement and bounce rate in the first week of sending, and start near the typical 14 emails per mailbox per day.

Methodology

More than 850 million emails sent through Smartlead, using combined, anonymous platform data only. Only senders with at least 500 emails sent in the period are included.