How to Warm Up a New Email Domain (And Why Skipping It Destroys Deliverability)

The short answer: Email domain warm-up is the process of gradually increasing your sending volume over 4–8 weeks so mail providers build a positive reputation for your domain before you send at scale. Start at 50–100 emails per day to your most engaged contacts, double the volume roughly weekly, and monitor open rates, spam complaint rates (keep below 0.08%), and hard bounce rates (keep below 2%). Skipping warm-up and sending thousands of emails on day one from a new domain will trigger spam filtering that can take weeks to recover from.

A new domain has no email sending history. To major mail providers — Gmail, Outlook, Yahoo — it's an unknown quantity. Unknown senders get scrutinised more carefully, and any signal of bulk or low-quality sending gets weighted heavily against a domain that hasn't yet built a reputation.

Send 5,000 emails on day one from a new domain and you'll almost certainly be filtered to spam — possibly permanently. Warm up gradually and you build a reputation that gets your emails delivered reliably at scale.

This guide explains how sender reputation works, what a correct warm-up timeline looks like, and how to know when it's working.

Why New Domains Go to Spam

Mail providers use reputation signals to decide where to deliver email. For established domains with years of clean sending history, those signals are strong and positive. For a new domain, there's no history at all.

In the absence of history, providers default to caution. A new domain sending high volumes immediately triggers several red flags:

No reputation — no prior signals to indicate this is a legitimate sender
High volume too fast — pattern consistent with spam campaigns that use fresh domains to evade filters
Low engagement rates — early emails to cold lists often go unopened, signalling to providers that recipients don't want them
Potential spam trap hits — purchased lists and unverified addresses frequently contain spam traps that, when hit, immediately damage new domain reputation

The result is that even well-intentioned, legitimate email from new domains can land in spam for weeks if no warm-up process is followed.

Before You Start Warming Up: Authentication First

Warm-up doesn't work without authentication. If your SPF, DKIM, or DMARC records are missing or misconfigured, no amount of gradual sending will build a good reputation — you're just gradually demonstrating you can't authenticate.

Before sending a single email from your new domain, confirm:

SPF record is published and includes every service that will send from your domain
DKIM signing is enabled on your email platform
DMARC record is published with at least p=none and a rua reporting address

A free Full Audit at EmailAudit.io checks all three in seconds. The SPF Generator, DKIM Generator, and DMARC Generator let you build each record from scratch if any are missing.

If you're setting up on Google Workspace, see the DMARC setup guide for Google Workspace. For Microsoft 365, see the Microsoft 365 authentication guide.

What "Warming Up" Actually Means

Warm-up is the process of starting with small daily sending volumes and increasing gradually over 4–8 weeks. The goal is to give mail providers time to observe your sending patterns and build a positive reputation signal based on engagement.

The key inputs reputation systems track:

Open rates — are recipients opening your emails?
Click rates — are they clicking?
Spam complaints — are recipients marking you as spam?
Unsubscribes — are they opting out in high numbers?
Bounce rates — are your emails reaching real addresses?

High opens and clicks, low complaints and bounces, consistent volume growth = trustworthy sender. The opposite, especially at high volumes before reputation is established, collapses deliverability quickly.

The Warm-Up Timeline

This schedule assumes you're sending to an engaged, opted-in list. Adjust downward if your list quality is uncertain.

Week	Daily Volume	Notes
1	50–100	Your most engaged recipients only — people who recently opened or clicked
2	200–500	Expand to recipients who've opened in the last 90 days
3	500–1,000	Continue with high-engagement segment
4	1,000–2,500	Broaden to full active list if engagement metrics are holding
5–6	2,500–5,000	Full list, monitoring closely
7–8	5,000–10,000+	Scale to full sending volume if no deliverability issues

Adjust based on signals: If open rates drop below 20% or spam complaints rise above 0.1%, slow down. Resume the prior week's volume for another week before advancing.

Which Recipients to Start With

The first emails from your new domain carry the most weight — they establish the baseline reputation. Prioritise:

Your own team — send internal emails first. These will open and not mark as spam.
Recent purchasers — high motivation to open transactional or post-purchase email
Recently active subscribers — opened or clicked within the last 30 days
Contacts who opted in manually — highest engagement expectation

Avoid during the warm-up period:

Contacts who haven't engaged in 6+ months
Purchased or rented lists
Addresses you're uncertain about (old imports, trade show badge scans, etc.)

What to Monitor During Warm-Up

Google Postmaster Tools

Set up Google Postmaster Tools for your domain from day one. It shows:

Domain reputation (low, medium, high, bad)
Spam rate — the percentage of your Gmail-delivered emails being marked as spam
Authentication compliance — DMARC pass rate for Gmail traffic

If reputation shows "bad" or spam rate exceeds 0.1%, stop sending immediately and investigate.

DMARC Aggregate Reports

With a rua tag configured, you'll receive daily DMARC reports showing authentication results for every source sending from your domain. During warm-up, check these to confirm all your sending sources are passing authentication consistently. See how to read DMARC aggregate reports for a guide to interpreting them.

Bounce Rates

Hard bounces (address doesn't exist) above 2% indicate list quality problems. Clean your list before sending to it at scale.

Spam Complaint Rate

A complaint rate above 0.08% (Gmail's threshold) will trigger deliverability problems. Above 0.1% starts causing systematic filtering.

Common Warm-Up Mistakes

Starting with too high a volume. The most common error. Even 1,000 emails on day one is too fast for a brand-new domain with no reputation. Start at 50–100.

Sending to your worst-quality contacts first. Counter-intuitive but true: the first signals matter most. Use your best list segment initially, not a blast to everyone.

Stopping and restarting. Inconsistent sending patterns look suspicious. Once you start the warm-up, send something every day — even a small internal test — to maintain continuity.

Not having authentication in place. As covered above: warm-up without authentication is pointless. Reputation can't build on an unauthenticated domain.

Rushing to the full list. The schedule above is a minimum. If metrics are weak, slow down. Reputation built gradually is durable; reputation shortcuts get penalised.

Warm-Up for Transactional Email vs Marketing Email

Transactional email (order confirmations, password resets, receipts) is easier to warm up — recipients actively expect and open it. Engagement rates are naturally high. You can progress through the schedule more quickly.

Marketing/newsletter email requires more care — recipients are less likely to open unsolicited email, and spam complaint rates are higher. Start conservatively and only accelerate when engagement metrics are strong.

If you're sending both types, consider using separate subdomains: mail.yourdomain.com for transactional and news.yourdomain.com for marketing. This way a complaint spike on marketing email doesn't damage your transactional reputation.

After Warm-Up: Maintaining Your Reputation

Sender reputation isn't a one-time achievement. It degrades if you:

Stop sending regularly and then restart at high volume
Let list hygiene lapse (accumulating hard bounces and disengaged subscribers)
Have a compromised sending account trigger spam complaints
Let authentication records lapse or break

Check your authentication records periodically. The free Security Score tool checks SPF, DKIM, DMARC, and blacklists in one pass — worth running before any major send if you haven't sent recently.

Related Guides

Check your authentication before you start sending — free Full Audit at EmailAudit.io. SPF, DKIM, DMARC, and blacklist checks in seconds. No account required.