How do I warm up a new IP address for transactional emails?
Michael Ko
Co-founder & CEO, Suped
Published 20 Jun 2025
Updated 17 Aug 2025
8 min read
When you launch a new email program or migrate to a new IP address, a critical step often overlooked for transactional emails is IP warming. While some might think that high-engagement transactional emails, such as password resets or account activations, don't require this process, that's a common misconception that can lead to deliverability issues.
Every new IP address starts with a neutral sender reputation. Mailbox providers, including Google and Yahoo, are cautious of sudden, high-volume sending from unknown IPs, regardless of the email type. They monitor sending patterns to determine if an IP is trustworthy or if it's potentially associated with spam. This is why a methodical warming process is essential.
The goal of warming a new IP address is to gradually build a positive sender reputation with internet service providers (ISPs) and mailbox providers (MBPs). This process involves sending increasing volumes of email over time, allowing providers to observe consistent, positive engagement from your sending IP. Failing to do so, even with transactional emails, can lead to messages being throttled, delayed, or worse, delivered to the spam folder, impacting critical user interactions.
Why IP warming is essential for transactional emails
IP warming, sometimes called IP address warm-up, is the process of slowly and methodically increasing the volume of email sent from a new IP address (or one that hasn't been used recently). This gradual ramp-up allows mailbox providers to recognize your sending patterns and establish a positive sender reputation. Think of it like building credit history: you start small and prove your reliability over time.
For transactional emails, this is particularly important because while they have inherently high engagement rates, a new IP still lacks a history. Mailbox providers prioritize delivering emails from IPs with established trust. Without a proper warm-up, even critical messages like password resets or order confirmations could face delays or be misclassified as spam, leading to a poor user experience and potential revenue loss.
A new dedicated IP, even when used exclusively for transactional emails, needs this warming period. Shared IPs often come pre-warmed, but a dedicated IP's reputation is entirely yours to build. This also means you have full control over your sending reputation, which is a significant advantage for high-priority transactional sends.
Building a solid reputation involves consistent sending with low bounce rates, minimal spam complaints, and strong engagement. This foundation ensures that your transactional emails land in the inbox reliably.
The risk of skipping IP warming
Skipping the IP warm-up process, even for transactional emails, can lead to severe deliverability problems. Your emails might be marked as spam by providers like Google, Yahoo, or Microsoft. This can result in significant delays or outright blocking of essential communications. It also makes it harder to recover domain reputation later. It's much easier to build a good reputation from scratch than to repair a damaged one.
Crafting your IP warming strategy
Even for transactional emails, a structured IP warming plan is crucial. The core principle is to start with low volumes and gradually increase them. This consistent, measured increase demonstrates legitimate sending behavior to mailbox providers, building trust over time. You are essentially proving that you are a responsible sender.
The great advantage of transactional emails for warming is their high engagement. Password resets, order confirmations, and account verifications typically have high open rates and low complaint rates because recipients are expecting and need these emails. This positive engagement signals to ISPs that your IP is sending desired mail, accelerating the reputation-building process. I often recommend starting with these high-priority, high-engagement messages.
A typical warming schedule for transactional emails might look something like the table below. It is not rigid, but it provides a framework. The key is to monitor your deliverability metrics closely during this phase and adjust your sending volume based on performance. If you see signs of trouble, like increased bounces or blocks, slow down your sending.
It is also beneficial to segment your recipients during warming, starting with your most engaged users. This ensures early positive interactions, reinforcing your good sender reputation.
Day
Daily Volume (Approx.)
Notes
1-3
1,000 - 5,000
Focus on highly engaged, critical transactional emails (password resets, OTPs).
4-7
5,000 - 15,000
Gradually add more transactional email types (order confirmations, shipping updates).
8-14
15,000 - 30,000
Continue to increase, monitoring engagement and bounce rates.
15-30
30,000+ (approaching full volume)
Reach target daily volume while maintaining high engagement. Monitor for blocklist appearances.
Practical steps for warming up
To effectively warm a new IP, begin by prioritizing the transactional email types that elicit the highest engagement and are most critical to your users. These include password reset emails, one-time passcodes (OTPs), account activation emails, and double opt-in confirmations. Their immediate relevance to the recipient ensures high open rates and low spam complaint rates, which are crucial for building trust with mailbox providers. If you are also warming a new sender address, this applies to that process as well.
Once you've identified your highest-engagement transactional emails, you can control the volume by gradually enabling these triggered campaigns. Instead of activating all transactional sends simultaneously, consider rolling them out in batches. For instance, you might start with just password resets, then add account activations a few days later, and then move to order confirmations. This phased approach allows you to manage the flow and observe how mailbox providers react.
Monitoring your performance closely is non-negotiable during IP warming. Keep a keen eye on your open rates, click-through rates, bounce rates, and, most importantly, spam complaint rates. Tools like Google Postmaster Tools are invaluable for this, offering insights into your domain and IP reputation. If you see any spikes in bounces or spam complaints, immediately reduce your sending volume and investigate the cause. This proactive approach helps prevent your IP from being added to a blocklist (or blacklist).
Authenticate your emails
Before you even start sending, ensure your email authentication protocols are correctly set up. This includes SPF, DKIM, and DMARC. Proper authentication helps mailbox providers verify that your emails are legitimate and from an authorized source, significantly improving your chances of inbox delivery during the warming phase and beyond.
SPF record: Defines which IP addresses are authorized to send emails on behalf of your domain. An example SPF record looks like this: "v=spf1 include:_spf.example.com ~all".
DKIM signature: Adds a digital signature to your outgoing emails, allowing the receiving server to verify that the email hasn't been tampered with and truly originated from your domain.
DMARC policy: Tells receiving servers what to do with emails that fail SPF or DKIM authentication, offering reporting capabilities for better visibility. You can generate a DMARC record and easily monitor your DMARC reports.
Avoiding common pitfalls and advanced considerations
A common pitfall during IP warming is trying to accelerate the process too quickly. Sudden spikes in email volume from a new IP are red flags for mailbox providers and can lead to immediate blocking or throttling. It’s far better to increase volume steadily and consistently, even if it feels slow. Remember, establishing trust takes time.
Another crucial consideration is separating your transactional email IP from your marketing email IP. Transactional emails typically have higher engagement and are less likely to trigger spam complaints, making them ideal for building a good sender reputation. Marketing emails, by nature, can have lower engagement and higher complaint rates, which could negatively impact the reputation of your transactional IP if they share the same address. Many providers recommend using separate IP addresses for these distinct sending types.
During the warming process, actively monitor various blocklists (also known as blacklists) to ensure your IP doesn't get listed. Early detection of a listing allows for quicker remediation, minimizing potential disruptions to your email flow. If your IP is added to a blocklist, it can severely impact your deliverability until you request its removal. Consider adding blocklist monitoring to your regular checks.
Dedicated IP
Requires a dedicated warming process, as its reputation is built from scratch based solely on your sending behavior.
Control: You have full control over your sending reputation.
Predictability: Performance is more predictable once warmed.
Risk: Your reputation is not affected by other senders.
Shared IP
Often comes pre-warmed due to collective sending history, but your reputation is influenced by other users.
Ease of Use: No manual warming required initially.
Reputation Risk: Poor sending practices by others can impact your deliverability.
Volume Limitations: May have volume caps to protect shared reputation.
Views from the trenches
Best practices
Start with the highest-engagement transactional emails like password resets and OTPs.
Implement SPF, DKIM, and DMARC before starting any sends.
Use separate dedicated IP addresses for transactional and marketing emails.
Common pitfalls
Sending high volumes too quickly from a new IP address, triggering spam filters.
Ignoring early signs of deliverability issues, such as increased bounces.
Using the same IP for both transactional and marketing emails, potentially mixing reputations.
Failing to implement proper email authentication, leading to messages being rejected.
Expert tips
Daily email volumes between 1,000 and 5,000 are generally safe to start with for transactional emails.
You might get away with higher initial volumes, around 50k, but it requires careful planning and monitoring.
If you have varying daily volumes, consider round-robinning or diverting overflow to a different IP.
For very large senders, strategic planning and extra IPs can allow for higher day-one volumes.
Expert view
Expert from Email Geeks says that new IP addresses still need warming, even if it's for transactional emails. It can be tricky, but sometimes low natural daily volume helps it warm itself. Otherwise, you must limit volume or use round-robin sending.
November 7, 2023 - Email Geeks
Expert view
Expert from Email Geeks says that you can gradually warm up a transactional IP by enabling triggered campaigns one by one, or in batches, depending on the volume. This might not be necessary if daily send volumes are consistently low and gradual.
November 7, 2023 - Email Geeks
Ensuring smooth transactional email delivery
Warming up a new IP address for transactional emails is not just a recommendation, it's a fundamental requirement for ensuring consistent email deliverability. While transactional emails benefit from high engagement, a new IP still needs to build trust with mailbox providers through a controlled, gradual increase in sending volume.
By following a strategic warming schedule, prioritizing highly engaged email types, and rigorously monitoring your sending metrics, you can establish a strong sender reputation. This proactive approach minimizes the risk of emails landing in the spam folder or being delayed, safeguarding critical communications with your users.
Investing time and effort into a proper IP warming strategy pays dividends in long-term deliverability and sender trustworthiness, ensuring your transactional emails consistently reach their intended recipients.
Google, 
Yahoo, or 
Microsoft. This can result in significant delays or outright blocking of essential communications. It also makes it harder to recover domain reputation later. It's much easier to build a good reputation from scratch than to repair a damaged one.
