What is the best strategy and duration for warming up a domain?
Matthew Whittaker
Co-founder & CTO, Suped
Published 5 Jun 2025
Updated 16 Aug 2025
6 min read
Establishing a strong sender reputation is crucial for successful email delivery. When you acquire a new domain or significantly change your email sending practices, Internet Service Providers (ISPs) view your domain with caution. This is where domain warming comes into play, a strategic process designed to build trust with mailbox providers over time.
Think of it like building a new relationship. You wouldn't suddenly start barraging someone with a thousand messages. Instead, you'd begin with polite, infrequent communication and gradually increase interaction as trust develops. Email sending works similarly, especially with major providers like Gmail and Yahoo Mail. A proper warm-up signals to them that you are a legitimate sender, not a spammer.
The goal is to gradually increase your sending volume while maintaining high engagement rates. This process demonstrates consistent, positive sending behavior, which is essential for avoiding spam filters and ensuring your messages reach the inbox.
Why domain warming is essential
Domain warming is not just a suggestion, it's a fundamental step for any new sender, or for those who have been inactive. Without it, you risk a swift descent into the spam folder, a scenario that can take a long time to recover from. A poor sending reputation means your emails will either be rejected outright or routed directly to the junk folder, severely impacting your communication efforts.
This is especially critical when you're moving to a new domain, even if you're using an already warmed IP address. Mailbox providers evaluate domain reputation separately from IP reputation, so even with a pristine IP, a new domain needs to earn its stripes. If you're migrating to a new ESP or rebranding with a new domain, warming is non-negotiable.
The risks of skipping warm-up
Immediate blocklists: Sending high volumes from a new domain can trigger spam traps and blocklists, hindering future deliverability.
Poor inbox placement: Emails are likely to land in spam folders, reducing your reach and engagement.
Damaged reputation: Once your domain has a bad reputation, it can take months or even years to restore.
Even for a small email list, warming is recommended. While the volume might be lower, the principles remain the same: gradual increase and consistent positive engagement signals are key to building trust.
Crafting your warm-up strategy
The best domain warming strategy is centered on a gradual, consistent increase in sending volume to highly engaged recipients. This isn't about rushing the process, but rather about methodically demonstrating good sending habits to ISPs. The foundation of any good strategy is to start slow and build momentum.
I recommend beginning with a very small volume, perhaps 50-100 emails per day, targeting your most active subscribers. These are the individuals who have recently opened or clicked your emails, as they are most likely to engage positively, which sends strong positive signals to Microsoft, Yahoo, and Gmailabout your sender reputation. Avoid sending to lists with more than 90 days of inactivity during the initial warm-up, as this can negatively impact your efforts.
Consistency is paramount. Stick to a regular sending schedule, ideally daily, even if it's just a small volume. This predictability helps ISPs recognize your domain as a consistent and reliable sender. As your engagement rates remain high and bounce rates stay low, you can gradually increase your daily sending volume by a small percentage, typically 5-10%.
Best practices
Start small: Begin with a minimal daily volume, around 50-100 emails.
Target engaged users: Send to recipients who have recently interacted with your emails.
Gradual increase: Increase volume by 5-10% daily as reputation improves.
Monitor metrics: Keep a close eye on open rates, click-through rates, bounce rates, and complaint rates.
Quality content: Ensure your emails are valuable and relevant to your audience.
Sending to unengaged lists: Targeting inactive users leads to low engagement and high complaint rates.
Ignoring metrics: Failing to monitor performance can lead to reputation issues going unnoticed.
Inconsistent sending: Irregular sending patterns can make your domain look suspicious.
Poor email content: Low-quality or irrelevant content will increase unsubscribe and spam complaint rates.
Another crucial aspect is maintaining excellent email hygiene. This means sending clean, high-quality emails that are free of spam trigger words and questionable content. Your emails should be well-formatted, personalized where appropriate, and provide value to the recipient. This helps in achieving strong engagement rates, which are key indicators of a healthy sender.
Duration and advanced considerations
The duration of a domain warm-up period can vary significantly, typically ranging from 4 to 12 weeks. There's no one-size-fits-all answer, as several factors influence this timeline. The size of your intended audience, the frequency of your sends, and the responsiveness of your recipients all play a role.
For smaller lists or less frequent sending, a 4-6 week period might suffice. However, if you plan to send to hundreds of thousands or millions of recipients, or if you encounter any deliverability issues during the process, it could extend to 8-12 weeks, or even longer. For instance, Postmark suggests a few weeks, while other sources recommend up to three months for more cautious approaches.
It’s vital to continually monitor your sending metrics throughout the warm-up period. Pay close attention to bounces, complaints, and engagement rates. If you notice a spike in bounces or complaints, or a dip in engagement, it's a clear signal to slow down your sending volume until the metrics improve. This adaptive approach ensures you're always responding to how mailbox providers are perceiving your traffic. Monitoring tools can provide insights into your domain reputation with key providers.
Example domain warm-up schedule
Domain: yourdomain.com
Sending Volume: Daily
Week 1: 50-100 emails to highly engaged users
Week 2: 100-200 emails, still highly engaged
Week 3: 200-400 emails, expand to engaged users within 60 days
Week 4: 400-800 emails, expand to engaged users within 90 days
Continue gradual increases, adjusting based on performance.
Remember that IP warm-up and domain warm-up are related but distinct processes. While a shared, already warmed IP can make domain warming easier, the domain itself still needs to build its own reputation. If you are also warming an IP address, the overall process can be more complex, especially when dealing with dedicated IPs.
Achieving optimal deliverability
A well-executed domain warm-up strategy is an investment that pays dividends in long-term email deliverability. It sets the stage for a strong sender reputation, ensuring your messages consistently reach your audience's inboxes. This foundational work helps you avoid common pitfalls like being placed on a blacklist (or blocklist) or having your emails routed to spam.
Patience and diligence are key. Resist the urge to accelerate the process, as this can undermine all your efforts. Continuous monitoring and a willingness to adjust your sending volume based on performance indicators will ensure a smooth and successful warm-up. Remember that even after warming, maintaining good sending practices is essential for sustained deliverability.
By following these guidelines, you can build a robust sending reputation for your domain, leading to improved inbox placement, higher engagement, and ultimately, more effective email campaigns. It's a proactive step that safeguards your email program and maximizes its impact, ensuring your messages always get through.
Views from the trenches
Best practices
Start domain warm-up slowly with small volumes to highly engaged recipients.
Segment your email lists carefully, prioritizing recent openers and clickers.
Consistently monitor key metrics like open rates, bounce rates, and complaints.
Pause or reduce sending volume if you observe negative reputation signals.
Ensure your email content is valuable and relevant to encourage engagement.
Common pitfalls
Increasing sending volume too quickly, leading to spam filter triggers.
Including inactive or unengaged recipients in the initial warm-up sends.
Ignoring daily monitoring of deliverability metrics.
Inconsistent sending schedules, which can appear suspicious to ISPs.
Failing to implement proper email authentication (SPF, DKIM, DMARC).
Expert tips
Leverage shared, pre-warmed IPs when possible to ease the domain warm-up.
Understand that Gmail's reputation assessment might take longer than others.
For very large audiences, be prepared for a warm-up period extending up to 12 weeks.
Consider creating a seed list with major ISP accounts for internal monitoring.
Warm-up is a continuous process, not just a one-time setup for new domains.
Expert view
Expert from Email Geeks says using shared, good IP addresses can simplify the domain warm-up process considerably.
2021-09-28 - Email Geeks
Expert view
Expert from Email Geeks says to start with the most active users, focusing on recent opens and clicks, as this sends positive signals to mailbox providers.
Gmail and Yahoo Mail. A proper warm-up signals to them that you are a legitimate sender, not a spammer.
Microsoft, Yahoo, and 
Gmailabout your sender reputation. Avoid sending to lists with more than 90 days of inactivity during the initial warm-up, as this can negatively impact your efforts.
