How to Warm Up a New Email Sending Domain

Why Domain Reputation Matters More Than IP Reputation

In the past, email reputation was primarily tied to IP addresses. Spammers would burn through IPs, so IP reputation was a useful signal. But as email infrastructure evolved (shared IPs, cloud hosting, frequent IP changes), ISPs shifted toward domain-based reputation. Gmail in particular now weights domain reputation as the primary factor in filtering decisions.

This means you cannot escape a bad reputation by switching email providers or moving to a new IP. Your domain reputation follows you. It also means that establishing a good domain reputation from the start is critical, because repairing it later is a slow and painful process.

When You Need Domain Warming

• Brand new domain: A domain registered recently that has never sent email. ISPs have zero data on it.
• New sending subdomain: If you set up mail.yourdomain.com specifically for marketing email. Even if yourdomain.com has reputation, the subdomain starts fresh.
• Domain that has not sent in months: If a domain was dormant for a long period, its reputation may have decayed. ISPs forget inactive senders.
• Domain switching from one use to another: If a domain was used for transactional email only and you start sending marketing email from it, the pattern change can trigger filtering.

Domain Warming Strategy

Before You Start Sending

• Set up complete authentication: SPF, DKIM, and DMARC.
• Make sure your domain has a working website with real content. ISPs check whether a sending domain has a legitimate web presence.
• Set up Google Postmaster Tools and Microsoft SNDS for your domain so you can monitor reputation from day one.
• Create a professional bounce and complaint handling system with webhook automation.

Week 1: Start Very Small

Send 50-200 emails per day to your most engaged subscribers. These should be people who have opened or clicked your email (from your existing domain or list) within the last 30 days. If you do not have existing engagement data, start with your most recent signups who are most likely to be active.

The goal in week 1 is to generate high open rates and zero complaints. Every open and click is a positive signal to ISPs that this new domain sends wanted email. Every complaint or bounce is a negative signal that is magnified because the domain has no history to offset it.

Week 2: Gradual Increase

Double your volume every 2-3 days. Move from 200 to 500 to 1,000 to 2,000 emails per day. Continue prioritizing engaged subscribers. Start mixing in moderately engaged subscribers (opened in last 90 days) as you reach the higher end of week 2 volumes.

Week 3-4: Ramp to Full Volume

Continue doubling until you reach your target daily volume. By week 3, you can start including your broader subscriber base. Monitor Google Postmaster Tools throughout. Your domain reputation should be building from "no data" to "Medium" or "High" during this period.

Ongoing: Maintain Consistency

After warming, maintain a consistent sending schedule. ISPs reward regular, predictable sending patterns. A sudden gap of several weeks followed by a large blast can trigger filtering even on a warmed domain.

Domain Warming vs IP Warming

The two processes are similar in approach (gradual ramp-up with engaged subscribers) but target different reputation systems:

• Domain warming is always needed for new sending domains, even on shared IPs that are already warm.
• IP warming is needed for new dedicated IPs but not for shared IPs that other senders are already using.
• If you have both a new domain and new dedicated IPs, you are warming both simultaneously. Follow the IP warming schedule (which is typically more conservative) and both will warm together.

Using a Subdomain for Marketing Email

A common best practice is to send marketing email from a subdomain like mail.yourdomain.com or news.yourdomain.com rather than from your root domain. This separates your marketing reputation from your corporate email reputation. If your marketing sends generate complaints or deliverability issues, they affect the subdomain's reputation without damaging your root domain (which handles business email through Google Workspace or Microsoft 365).

The subdomain still benefits from some of the root domain's age and authority, so warming is faster than with a completely new domain. However, ISPs treat subdomains as somewhat independent entities, so you still need to go through the warming process.