What is the best IP warmup strategy for email sending?
Matthew Whittaker
Co-founder & CTO, Suped
Published 17 Apr 2025
Updated 16 Aug 2025
7 min read
When you're launching a new email program or migrating to a new IP address, building a strong sender reputation is paramount. Imagine moving into a new neighborhood where no one knows you. You wouldn't throw a massive, noisy party on day one, would you? Email service providers (ISPs) like Google and Microsoft operate similarly, relying on your sending behavior to determine if you're a trustworthy sender. This is where IP warmup comes into play.
IP warming is the strategic process of gradually increasing the volume of email sent from a new or cold IP address. This slow and steady approach allows ISPs to observe your sending habits, engagement rates, and overall list quality. Without a proper warmup, attempting to send a large volume of emails immediately can be detrimental. ISPs, wary of potential spam, might throttle your emails, route them to the spam folder, or even place your IP on a blocklist (or blacklist), severely impacting your deliverability.
A well-executed IP warmup strategy builds trust, improves your sender reputation, and ensures your legitimate emails consistently reach the inbox. It's a foundational step for any sender aiming for high deliverability rates and a healthy email program.
Foundation of a strong IP warmup strategy
The cornerstone of any effective IP warmup strategy is to begin with low sending volumes to your most engaged subscribers. These are the recipients who are most likely to open, click, and interact positively with your emails. This initial positive engagement sends strong signals to ISPs, indicating that your mail is wanted and valued. Transactional emails, like password resets or order confirmations, are often ideal for this phase due to their inherently high engagement. For more detailed insights into this approach, consider reviewing best practices for transactional emails.
Before you even start sending, prioritize rigorous list hygiene. A clean email list is critical for preventing bounces and avoiding spam traps, which can instantly damage a new IP's reputation. Utilize validation tools to remove invalid or risky addresses. This proactive step helps maintain a healthy sending environment from the outset.
Finally, ensure your email authentication protocols—SPF, DKIM, and DMARC—are correctly configured. ISPs heavily rely on these records to verify your identity as a legitimate sender. Proper authentication is a prerequisite for good deliverability and is essential during the sensitive IP warmup phase. You can find a simple guide to DMARC, SPF, and DKIM for reference.
Prepare your sending environment
Engaged segments: Start with the most active subscribers who consistently open and click.
List hygiene: Validate and clean your email list to remove invalid addresses and spam traps.
Authentication setup: Correctly configure SPF, DKIM, and DMARC records.
Implementing your warmup schedule
The core of IP warming involves a methodical, gradual increase in your email sending volume. There's no one-size-fits-all schedule, as it depends on your target volume, list quality, and audience engagement. However, the general principle is to start small and incrementally increase the number of emails sent each day or week. A typical warmup period can range from two to four weeks, but larger volumes may require more time. You can learn more about this process from Twilio SendGrid's email guide to IP warmup.
Careful audience segmentation is key. Begin your warmup by sending to your most active and engaged segments. These are the subscribers who have recently opened or clicked your emails. As your reputation builds, you can gradually expand to less engaged but still legitimate segments of your list. Avoid sending to disengaged or unverified contacts during this sensitive phase, as negative interactions can quickly derail your progress.
The content you send during warmup also matters significantly. Prioritize high-engagement emails such as welcome series, transactional messages, or updates that recipients are expecting. These types of emails tend to generate positive metrics like high open and click rates and low complaint rates, which are crucial for establishing a good sender reputation. Avoid promotional or less-expected content until your IP is fully warmed up.
It's important to understand that IP warming is not just about increasing volume, but about increasing engaged volume. If your engagement dips during the ramp-up, it's a signal to slow down. Maintaining consistent positive engagement is more important than rigidly following a predefined schedule. For a comprehensive look at scaling email volume, refer to best practices for volume scaling.
Constant monitoring of your email performance is non-negotiable during IP warmup. Key metrics to track include open rates, click-through rates, bounce rates, and crucially, spam complaint rates. High engagement metrics signal positive sender behavior to ISPs, while spikes in bounces or complaints are red flags. Tools like feedback loops and postmaster tools (e.g., Google Postmaster Tools) provide invaluable insights into how ISPs perceive your sending. It is also beneficial to leverage an email blocklist monitoring tool to ensure your IP doesn't end up on any public blocklists (or blacklists).
If you encounter any issues—such as a sudden drop in deliverability, increased spam complaints, or throttling by an ISP—be prepared to adapt your strategy. This might mean temporarily slowing down your sending volume, re-evaluating your audience segmentation, or refining your content. Addressing these issues swiftly prevents long-term damage to your sender reputation. For more on what causes deliverability issues, read about why emails fail.
Remember, IP warming isn't a one-time task; it's the initial phase of an ongoing commitment to maintaining good sender reputation. Once your IP is warmed, consistency in sending volume, adherence to best practices, and continued monitoring are crucial for sustained inbox placement. Think of it as establishing a good credit score—it requires careful management over time.
Risks of aggressive warming
High bounce rates: ISPs may quickly flag sudden, large volumes to unknown recipients, leading to bounces.
Blocklisting: Your IP could be added to blocklists (or blacklists) if perceived as a spam source, blocking future sends.
Reputation damage: Long-term harm to sender reputation, making it difficult to reach the inbox.
Benefits of a measured approach
Stronger reputation: Builds trust with ISPs, leading to better deliverability.
Better inbox placement: Higher likelihood of emails landing in the primary inbox.
Long-term success: Establishes a sustainable email sending program.
Views from the trenches
Best practices
Start with highly engaged segments to generate positive feedback and build trust with ISPs.
Prioritize list hygiene by validating and cleaning your email list to prevent bounces and spam trap hits.
Ensure all email authentication records (SPF, DKIM, DMARC) are correctly configured before you begin sending.
Monitor engagement metrics closely, such as open and click rates, and adjust your sending volume accordingly.
Common pitfalls
Sending too large a volume too quickly can trigger spam filters and lead to immediate blocklisting (or blacklisting).
Ignoring low engagement rates during the warmup can signal poor list quality and harm your sender reputation.
Failing to clean your email list can lead to high bounces and spam trap hits, negatively impacting deliverability.
Inconsistent sending patterns can hinder the warming process and make it difficult for ISPs to assess your reputation.
Expert tips
Align your warmup schedule with your long-term sending volume and frequency goals for a seamless transition.
Utilize transactional emails for their naturally high engagement during initial warmup phases, sending positive signals.
Leverage ISP feedback loops to gain insights into your sending performance and address any emerging issues proactively.
Consult historical data and industry benchmarks on warming volumes to inform and refine your strategy.
Expert view
Expert from Email Geeks says: If your target volume is very high, sending as few as 50 or 125 subscribers is insufficient for a proper warmup.
2022-04-22 - Email Geeks
Marketer view
Marketer from Email Geeks says: Both methods of gradually adding subscribers or sending to new segments daily are acceptable, provided email volume grows alongside good engagement.
2022-04-22 - Email Geeks
Achieving email deliverability success
Implementing the best IP warmup strategy for email sending is a critical investment in your email marketing success. It's not merely a technical task, but a strategic imperative that directly impacts your deliverability, sender reputation, and ultimately, your campaign performance. By patiently building trust with ISPs, you lay the groundwork for consistent and reliable email delivery.
Remember the core principles: start small with highly engaged audiences, meticulously clean your lists, ensure proper authentication, and continually monitor your sending metrics. Be prepared to adjust your strategy based on feedback from ISPs, and don't rush the process.
A well-executed warmup isn't just about avoiding the spam folder, it's about maximizing your inbox placement and ensuring your messages consistently reach their intended recipients, fostering stronger connections with your audience.
Google and 
Microsoft operate similarly, relying on your sending behavior to determine if you're a trustworthy sender. This is where IP warmup comes into play.
