How to warm up a new domain when moving email marketing and transactional emails to it?
Matthew Whittaker
Co-founder & CTO, Suped
Published 12 Aug 2025
Updated 16 Aug 2025
6 min read
Moving to a new website domain is an exciting venture, and transferring your email infrastructure alongside it requires careful planning. This includes both your marketing campaigns and essential transactional emails. The goal is to ensure a seamless transition that maintains your sender reputation and deliverability rates, preventing your messages from landing in spam folders or being blocked entirely.
A key part of this move involves what's known as domain warming. It’s a critical process to introduce your new domain to mailbox providers (like Gmail and Outlook) in a controlled manner. Done correctly, it builds trust, ensuring your emails reach the inbox without issues. Neglecting it can lead to severe deliverability problems, regardless of how good your content is.
What is domain warming?
Domain warming is the methodical process of sending email from a new or previously unused domain, starting with low volumes and gradually increasing them over time. This approach helps mailbox providers recognize your domain as a legitimate sender, building a positive sender reputation. It signals that you are not a spambot but a legitimate organization sending wanted mail.
The reasoning behind this is simple, but crucial. Mailbox providers analyze various signals to determine if an email is legitimate or spam, and sending volume is a big one. A sudden surge of emails from a brand-new domain raises red flags, often leading to your emails being routed to the spam folder or rejected outright. This applies even if you are using shared IP addresses, as domain reputation is distinct from IP reputation.
While both domain and IP warming contribute to deliverability, a domain warm-up is essential when migrating to a new domain, even if your underlying IP (or shared IP pool) is already warm. You are introducing a new identity to the email ecosystem. Think of it as introducing yourself to a new neighborhood: you start by greeting a few neighbors before hosting a block party.
The strategic separation of email types
One of the most effective strategies for maintaining strong deliverability, especially during a domain migration, is to separate your email streams. This means using distinct subdomains for marketing emails (e.g., e.yournewsite.com) and transactional emails (e.g., yournewsite.com or mail.yournewsite.com). This separation is a critical best practice that isolates the reputation of different email types.
The primary benefit of separating these streams is risk mitigation. Marketing emails, by their nature, tend to generate higher complaint rates and lower engagement compared to transactional emails. If your marketing emails encounter deliverability issues, having them on a separate subdomain prevents these problems from directly impacting the deliverability of your critical transactional messages, such as order confirmations or password resets. This is why it is often recommended to move marketing emails to a subdomain.
Transactional email
Nature: User-initiated, expected, and typically high engagement. Examples include receipts, password resets, shipping notifications.
Domain Strategy: Often sent from the root domain or a dedicated subdomain, especially if using dedicated IPs.
Marketing email
Nature: Bulk sends, promotional, can have varying engagement levels and higher complaint rates.
Warm-up: Mandatory process involving gradual increases in volume to build trust and avoid blacklists (blocklists).
Domain Strategy: Always recommended to use a separate subdomain to protect your core domain’s reputation.
A phased approach to domain warm-up
For marketing emails, begin your warm-up by sending to your most engaged contacts. These are subscribers who consistently open and click your emails. Their positive engagement signals to mailbox providers that your emails are valued, helping to build a good initial reputation for your new domain. Start with a small percentage of your most active list and gradually increase the volume.
A 30-day period can be sufficient for warming up a new domain, especially on shared IPs, if done strategically. The key is consistency and careful monitoring. The general rule is to start with low volumes (e.g., 5,000-10,000 emails per day) and gradually increase by 10-20% daily or every few days, depending on engagement metrics. Here is a sample plan:
Period
Daily volume
Week 1
5,000-10,000
Week 2
10,000-25,000
Week 3
25,000-50,000
Week 4+
Gradual increase to full volume
For transactional emails, a dedicated warm-up often isn't necessary because these emails are expected and have high engagement rates. However, ensure they are truly transactional in nature and don't contain any promotional content, as this can negatively impact their reputation. If you're migrating your email platform, consult with your new provider for a tailored warm-up plan, especially if moving to dedicated IP addresses.
Essential technical setups and monitoring
Before sending any emails from your new domain, ensure all necessary DNS records are properly configured. This includes SPF, DKIM, and DMARC records. These authentication protocols verify that your emails are legitimately from your domain and help prevent spoofing and phishing attempts. Incorrect configurations can lead to immediate deliverability failures, so thorough testing is essential.
During the warm-up period, focus on sending high-quality, relevant content to your engaged audience. Avoid anything that might trigger spam complaints. This means no unsegmented cold outreach or risky content. Regularly clean your email list to remove inactive subscribers and hard bounces. Additionally, ensure your unsubscribe links are prominent and functional, complying with regulations like CAN-SPAM (30 days post-send) and CASL (60 days).
Constant monitoring of your email performance is non-negotiable. Pay close attention to your open rates, click-through rates, bounce rates, and crucially, your spam complaint rates. Utilize Google Postmaster Tools and other analytics provided by your email service provider. Keep a watchful eye on email blocklists (blacklists) to catch any issues early. Promptly address any spikes in complaints or bounce rates, as these indicate potential problems with your warm-up or list quality.
Monitoring critical metrics
During your domain warm-up, closely track your deliverability metrics. A sudden increase in bounces or spam complaints suggests you might be increasing your volume too quickly or sending to unengaged contacts. Be ready to adjust your sending schedule and list segmentation based on these indicators. Early detection of issues is crucial for successful domain warming.
Views from the trenches
Best practices
Start domain warming with your most engaged subscribers to generate positive signals for mailbox providers.
Separate marketing emails to a dedicated subdomain to protect the reputation of your main domain.
Pre-warn your existing audience about the domain change and offer a chance to reconfirm their subscription.
Common pitfalls
Sending too high a volume too quickly from the new domain, leading to immediate spam flagging.
Failing to separate transactional and marketing email streams, risking critical transactional email deliverability.
Neglecting to monitor deliverability metrics like bounce rates and spam complaints during the warm-up.
Expert tips
Domain warming typically takes less time than IP warming, especially on shared IPs with good reputations.
Transactional emails, if truly transactional, generally do not require a formal warm-up period.
Consider a longer transition period, like 3 months, for large migrations to allow for gradual shifts.
Marketer view
Marketer from Email Geeks says to mail your very best, most engaged users first, as domain warm-ups depend heavily on how subscribers react to emails from the new domain. If engagement is positive, the process will be smoother.
February 1, 2023 - Email Geeks
Expert view
Expert from Email Geeks says it is definitely easier to warm a new domain on a shared IP, provided that shared IP has a good reputation. They also advised separating transactional emails to a different subdomain because marketing emails can still impact the overall top-level domain reputation if they are egregious.
February 2, 2023 - Email Geeks
Achieving a smooth email transition
Moving your email operations to a new domain is a significant undertaking that impacts your ability to reach customers. By understanding the principles of domain warming, strategically separating your marketing and transactional email streams, and diligently following a phased warm-up plan, you can minimize disruption and protect your sender reputation. A 30-day period can be feasible for domain warming, but it demands consistent effort and proactive monitoring.
Always prioritize the health of your email program. Building and maintaining a strong sender reputation is a continuous process that ensures your messages land in the inbox, fostering trust and engagement with your audience.
Outlook) in a controlled manner. Done correctly, it builds trust, ensuring your emails reach the inbox without issues. Neglecting it can lead to severe deliverability problems, regardless of how good your content is.
