How to warm up a new email domain for cold email
Updated 17 October 2026 · 6 min read
Short answer
Warm up a new domain by sending a small, slowly rising number of emails from each mailbox that get opened and replied to, starting around 2–5 a day and reaching about 30 a day over roughly three weeks, before you start cold campaigns. Keep warmup running at a lower level after campaigns start, and slow down if bounces or spam placement rise. Warmup builds a sending history; it cannot fix bad lists, irrelevant copy or high complaint rates.
Why new domains need warmup
Mailbox providers decide where mail goes partly on the sender's history. A domain registered last week has none, so a sudden jump from zero to hundreds of emails a day looks like the behaviour of a spammer. Warmup gives the domain and each mailbox a gradual, normal-looking history first.
A typical 21-day ramp
Exact numbers vary by tool; the shape matters more than the precise figures. This is the kind of ramp ReplyDak uses, from about 2 to 30 emails per mailbox per day over roughly 21 days:
| Days | Warmup emails per mailbox per day | Cold emails |
|---|---|---|
| 1–3 | 2–5 | None |
| 4–7 | 5–10 | None |
| 8–14 | 10–20 | None |
| 15–21 | 20–30 | None, or a handful to a very clean list near the end |
| 22+ | Keep 10–20 warmup emails a day running | Start at 10–20/day, rise toward 30 over 1–2 weeks |
How to warm up a domain
- 1
Finish authentication first
Publish SPF, DKIM and DMARC and confirm they pass before the first warmup email. See SPF, DKIM and DMARC for cold email.
- 2
Make the mailbox look real
Use a real person's name, add a profile photo and a simple signature, and redirect the domain to your website.
- 3
Turn on warmup at a low volume
Start each mailbox at 2–5 warmup emails a day. A warmup tool exchanges messages with other real mailboxes, which open them, reply and move them out of spam.
- 4
Ramp slowly for about three weeks
Increase gradually toward ~30 a day. Avoid big jumps from one day to the next.
- 5
Start cold sending small
Begin with 10–20 cold emails a day per mailbox to a verified list, keep warmup running, and raise volume only while bounces and spam placement stay low.
- 6
Watch the signals and slow down if needed
If bounces, spam placement or complaints rise, drop volume or pause that mailbox and let warmup run for a few more days.
What warmup does and doesn't do
| Warmup does | Warmup doesn't |
|---|---|
| Builds a gradual sending history for new domains and mailboxes | Make an unauthenticated domain trustworthy |
| Creates opens, replies and not-spam signals on your mail | Fix a list full of invalid addresses or spam traps |
| Lets you spot DNS or reputation problems before real campaigns | Offset real recipients marking your cold email as spam |
| Keeps a baseline of positive engagement during campaigns | Guarantee inbox placement |
Health signals to watch
| Signal | Healthy | Act when |
|---|---|---|
| Hard bounce rate | Under 1–2% | Above ~3%: stop, re-verify the list |
| Warmup inbox placement | Most warmup mail lands in inbox | Placement drops noticeably over several days |
| Spam rate (Google Postmaster Tools) | Under 0.1% | Approaching 0.3%, Gmail's stated limit |
| Reply rate on cold campaigns | Stable or rising | Falls sharply with no change in copy or list |
| Blocklist checks | Not listed | Domain or IP appears on a major blocklist |
The 0.3% spam-rate ceiling and 0.1% target come from Google's sender guidelines; Yahoo also asks senders to stay below 0.3%. The bounce thresholds above are practitioner guidance, not published provider limits.
How ReplyDak handles warmup
Warmup is included with every ReplyDak mailbox. It starts automatically once DNS is in place, ramps from about 2 to 30 emails a day over roughly 21 days, and slows down or pauses a mailbox automatically if bounces, spam placement or complaints rise. Plans start at $2.69 per mailbox; see pricing.
ReplyDak does all of this automatically, in about 10 minutes.
Domains, DNS, Google Workspace mailboxes and warmup. From $2.69 per mailbox ($35 for 10).
FAQ
How long does it take to warm up a new email domain?
Plan on about three weeks before cold sending at meaningful volume, then a further one to two weeks of gradual increases. Older domains with clean history can sometimes move faster.
Is email warmup still necessary in 2026?
For new domains and mailboxes, yes. Providers have no history to judge them on, and a gradual ramp is safer than going from zero to full volume.
Should I keep warmup on after starting campaigns?
Yes. Keep a lower level of warmup running alongside campaigns so each mailbox keeps receiving positive engagement.
Can warmup fix a domain that is already in spam?
Sometimes it helps, combined with pausing cold sends, cleaning the list and fixing authentication. If the domain is badly damaged, it is often faster to rest it and move volume to fresh warmed domains.