IP Warm-Up Best Practices for Cold Email

Silvio Bonomi
16 minutes ago
14 min read

When sending cold emails from a new IP, you can't skip warming it up. ISPs closely monitor new IPs to prevent spam, so gradually increasing your email volume is key to building trust and ensuring your messages land in inboxes. Here’s what you need to know:

Start Small: Send 50–100 emails daily to engaged contacts, then increase volume over 15–60 days.
Authentication Is Critical: Set up SPF, DKIM, DMARC, and BIMI to prove your emails are legitimate.
Focus on Quality: Use clean, verified email lists. Avoid purchased or outdated contacts.
Monitor Metrics: Track open rates, spam complaints, and bounce rates to adjust as needed.
Consistency Matters: Stick to a regular sending schedule to build a reliable reputation.

Skipping these steps can lead to blacklisting, spam issues, and wasted effort. A methodical approach ensures better deliverability and stronger results for your cold email campaigns.

IP Warm-Up Basics

What is IP Warm-Up?

IP warm-up is the process of gradually increasing the number of emails sent from a new or "cold" IP address to establish a positive sender reputation with Internet Service Providers (ISPs). This step-by-step approach helps ISPs recognize your legitimacy as a sender.

The process typically begins with sending 50 to 100 emails per day during the first week, followed by a steady, planned increase in volume over the following weeks. By doing this, you demonstrate consistent and reliable sending behavior, which is critical for gaining trust. ISPs closely monitor your activity, especially once you start sending around 100 emails per day, to determine whether your emails end up in inboxes or are flagged as spam.

The entire warm-up process usually takes between 15 and 60 days. However, for businesses aiming to send thousands of emails daily, this period might extend to four to eight weeks. A common strategy is to double your email volume every few days, adjusting the pace based on the size of your email list and the engagement levels of your recipients.

This gradual increase is especially important for cold email campaigns, where reputation plays a key role in ensuring your emails are delivered successfully. Mastering this process is essential for achieving cold email success.

Why IP Warm-Up is Required for Cold Email

For cold email campaigns, IP warm-up is a critical step to overcome the initial scrutiny from ISPs. A new IP address starts with no sender reputation, and warming it up builds the trust necessary to ensure your emails reach the intended recipients.

Without an established reputation, cold emails are more likely to be flagged as spam. During the warm-up phase, ISPs monitor various factors like email volume, engagement rates, bounce rates, complaint levels, and the quality of your contact lists to assess your credibility. While some emails might initially land in spam folders, consistent positive engagement over time improves deliverability.

For B2B cold email campaigns, ensuring emails reach decision-makers is essential. Skipping or mishandling the warm-up process can lead to serious issues, such as high bounce rates, increased spam complaints, blocked emails, and long-term damage to your sender reputation.

Once you've built a strong sender reputation, you can confidently send emails to larger audiences without triggering spam filters. This reliability is crucial for sustained lead generation and business growth. For B2B outbound professionals, IP warm-up isn't just a technical step - it's a vital foundation for maintaining consistent and effective communication with prospects. Providers like Artemis Leads, known for their expertise in B2B outbound lead generation, stress the importance of a structured IP warm-up process to help cold email campaigns successfully reach decision-makers.

The Ultimate Guide to Cold Email Warmup & Deliverability in 2026

Setting Up for IP Warm-Up: Technical and Strategic Requirements

Your IP warm-up's success hinges on getting the technical setup and strategy right. These elements are crucial for building trust with Internet Service Providers (ISPs) and ensuring your emails actually reach inboxes.

Required Technical Setup for Email Authentication

Email authentication is non-negotiable. It’s how you prove to ISPs that your emails are legitimate. Without it, your messages are likely to be flagged or blocked. You’ll need to configure four key protocols: SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), DMARC (Domain-based Message Authentication, Reporting & Conformance), and BIMI (Brand Indicators for Message Identification).

Here’s a quick breakdown of what each protocol does:

SPF: Identifies which mail servers can send emails on your behalf, preventing domain spoofing.
DKIM: Adds a digital signature to verify that the email hasn’t been altered during transit.
DMARC: Aligns SPF and DKIM results, tells ISPs how to handle authentication failures, and provides reports on those failures.
BIMI: Lets your brand logo appear in supported inboxes when emails pass authentication checks.

Technical Requirement	Purpose	Best Practice
SPF	Confirms authorized senders	Publish SPF records in DNS before sending emails
DKIM	Ensures email integrity	Enable DKIM signing for all outgoing emails
DMARC	Manages SPF/DKIM failures & provides reports	Activate DMARC with reporting enabled
BIMI	Boosts brand visibility in inboxes	Set up BIMI for greater brand recognition

If your authentication records are missing or misconfigured, ISPs will likely block your emails or send them straight to spam. This is especially true for new IP addresses, where trust hasn’t yet been established.

Once your authentication is set up, focus on building a high-quality contact list.

Building a Clean and Engaged Contact List

Your contact list is just as important as your technical setup. Start with recipients who’ve opted in and are likely to engage with your emails. Positive engagement - like opens and clicks - signals to ISPs that your emails are welcome, which improves your reputation and deliverability.

For the initial warm-up phase, target recent signups or users who’ve interacted with your emails in the last 30 days. These contacts are more likely to respond positively. Stay away from purchased lists, scraped data, or outdated databases that haven’t been cleaned in a while.

If you’re running B2B cold email campaigns, focus on defining your Ideal Customer Profile (ICP). This helps you zero in on the right companies and decision-makers. By qualifying prospects carefully, you can include only high-potential leads, increasing engagement rates.

Take a page from Artemis Leads, which emphasizes list quality during IP warm-ups. They define ICPs, qualify leads, and use personalized outreach to create highly engaged contact lists. Using real team members’ names in outreach emails can also build trust and boost response rates. Pairing email outreach with LinkedIn can further increase your chances of connecting with prospects through their preferred channels.

Infrastructure Setup and List Hygiene

Even the best technical setup and contact list won’t work without reliable email infrastructure. Here’s what you need:

A dedicated sending IP for consistent email delivery.
Properly configured authentication protocols.
Integration with a reputable email service provider (ESP) that supports warm-up processes.

Make sure every email includes a working unsubscribe link. Process unsubscribe requests immediately, and regularly clean your list by removing invalid addresses or contacts with low engagement. Ignoring this step can lead to high bounce rates and spam complaints.

Keep an eye on your domain’s reputation using tools like Google Postmaster Tools and other monitoring services. Regularly check blacklists to ensure your IP and domain aren’t flagged by ISPs or security providers.

For automated list validation, tools like ZeroBounce and NeverBounce can help. Many ESPs also offer warm-up automation tools to simplify the process, ensuring consistent sending patterns and helping you monitor engagement effectively.

Skipping these steps can lead to high bounce rates, spam complaints, or even blacklisting - issues that could permanently damage your sender reputation. Laying a strong foundation now will set you up for success in your cold email campaigns.

Step-by-Step Guide to Warming Up an IP Address

Once your technical setup is complete and your email list is clean, it's time to start warming up your IP address. This process involves gradually increasing your email volume to build trust with Internet Service Providers (ISPs) and establish a solid sender reputation.

Start Small: Focus on Highly Engaged Contacts

Begin by sending 100 emails per day to your most engaged recipients. ISPs typically evaluate new IPs starting at this volume.

To maximize engagement, target contacts who have interacted with your emails in the past 30 days. Transactional emails - like purchase receipts, account updates, and welcome messages - are particularly effective for this stage since they tend to generate high open rates. If you're running B2B campaigns, prioritize recent signups or prospects who have shown clear interest in your services.

Avoid using inactive or purchased lists. Even a small number of spam complaints or high bounce rates can harm your IP's reputation early on. Building trust with ISPs from the start is essential for scaling up successfully.

Gradually Increase Volume Over Time

Once you've established a pattern of positive engagement, begin increasing your email volume gradually over a period of 15 to 60 days, depending on your ultimate sending goals. A common strategy is to double your daily send volume every few days, but only if your engagement metrics remain strong and complaint rates stay low.

For example, if your goal is to send 10,000 emails per day, your schedule could look like this:

Day 1: 100 emails
Day 2: 200 emails
Day 3: 400 emails
Day 4: 800 emails
Days 5–7: 1,600–6,400 emails
Day 8+: Gradually ramp up to 10,000 emails

For businesses aiming to send over 1,000,000 emails daily, extend the warm-up period to 60 days. When expanding your list, introduce less active or older segments in small increments - about 10–25% of your total list at a time.

Throughout this process, monitor your metrics and maintain consistent engagement to ensure a smooth ramp-up.

Stay Consistent and Monitor Engagement

Consistency is key during the warm-up phase. ISPs look for regular sending patterns to build trust in your IP's reputation. Whether you choose to send emails daily or spread them evenly across the week, stick to a predictable schedule. Erratic sending patterns can lead to delays in the warm-up process or cause your emails to land in spam folders.

Keep a close eye on daily metrics such as opens, clicks, bounces, unsubscribes, and complaints. High engagement rates (like opens and clicks) signal to ISPs that your emails are well-received, while low bounce and complaint rates indicate good list hygiene.

If you encounter minor bulking (emails landing in spam), don’t panic - it’s a common issue early on and often resolves as engagement improves. However, if major deliverability problems arise, reduce your sending volume and focus on your most engaged contacts until the issues are resolved. Pausing and addressing technical or list hygiene problems may be necessary to protect your sender reputation.

For B2B campaigns, leveraging services like Artemis Leads can be a game-changer. They specialize in identifying ideal customer profiles and qualifying prospects, ensuring your contact list stays highly engaged. By combining personalized email outreach with LinkedIn interactions, they help boost positive engagement, which strengthens your IP reputation.

Lastly, use a combination of your email service provider’s analytics and external reputation monitoring tools to track your progress and make data-driven adjustments as needed.

Monitoring and Managing IP Reputation

Keeping tabs on your IP's performance during the warm-up phase is essential for ensuring your emails land in inboxes instead of spam folders. Internet Service Providers (ISPs) assign a reputation score to your IP address, which plays a major role in determining deliverability. Without close monitoring, you might miss early signs of trouble.

Key Metrics to Track During Warm-Up

Use your email service provider's analytics dashboard daily to monitor critical metrics like open rates, click-through rates, bounce rates, spam complaints, unsubscribe rates, and blacklist status. High open and click-through rates show good engagement, while high bounce or complaint rates point to deliverability issues. Keep in mind that most ISPs won't actively monitor new senders until you're sending around 100 emails per day, making this a good threshold for collecting meaningful data.

Set up automated alerts for bounces and spam complaints so you can address problems quickly. For blacklist monitoring, tools like MXToolbox or Talos Intelligence can be invaluable. During the warm-up phase, check your blacklist status weekly, and once you're past this stage, a monthly review should suffice. This regular tracking allows you to tackle issues before they escalate.

Fixing Deliverability Issues

Two common problems during IP warm-up are bulking (emails being marked as spam) and blocking (emails being outright rejected by ISPs). Bulking often shows up as a sudden drop in open rates or reports of emails going to spam folders. If this happens on a small scale, continue sending to your most engaged recipients - it often resolves after a few sends.

Blocking is a more serious issue, usually signaled by bounce messages indicating rejection by the recipient's server. If blocking occurs, reduce your sending volume and focus solely on engaged users. Segment your list to include only recent engagers and slowly increase your sending volume as engagement improves. Properly configuring your SPF, DKIM, and DMARC records is also crucial, as incorrect settings can lead to both bulking and blocking issues. Addressing these problems promptly helps safeguard your IP reputation.

Ongoing Reputation Management After Warm-Up

Once your IP is warmed up, maintaining your reputation becomes a continuous process. Regularly clean your email list by removing addresses that bounce or show no engagement. Use double opt-in methods for new subscribers and stick to consistent sending schedules. It's also a good idea to periodically review your data management practices, as ISPs frequently update their filtering criteria.

For B2B campaigns, services like Artemis Leads can help refine your prospect lists and maintain high engagement levels. Many email platforms include built-in tools for reputation monitoring, while third-party options like Warmup Inbox, MailReach, and automated diagnostics offer additional support.

If your IP ends up on a blacklist, act quickly. Investigate the root cause - whether it's high complaint rates, technical missteps, or poor list hygiene - and resolve the issue. Once fixed, you can request removal from the blacklist provider. Most reputable providers will delist your IP once they see the problem has been addressed.

Common Mistakes and Best Practices for IP Warm-Up

After setting up your technical infrastructure and following the step-by-step warm-up guide, it’s important to recognize where businesses often falter and how to avoid those pitfalls. Even with the best intentions, mistakes during the IP warm-up process can cause serious setbacks. Let’s break down the common errors and highlight strategies that can help you maintain a strong IP reputation.

Common Mistakes to Avoid

One of the biggest missteps is increasing email volume too quickly. For example, a B2B SaaS company that sent 10,000 emails to an unsegmented list saw their open rates drop below 5%, while bounce rates spiked to over 10%. This led to blacklisting, and the recovery process involved months of list cleaning and starting the warm-up process all over again.

Another frequent mistake is using unverified or purchased email lists. These lists often contain outdated addresses, spam traps, or disengaged contacts, which can lead to high bounce rates and complaints. Such negative signals can cause ISPs to blacklist your IP before it even has a chance to warm up.

Inconsistent sending patterns are another common problem. For instance, sending 500 emails on one day, skipping a few days, and then blasting 2,000 emails later in the week confuses ISPs and damages your sender reputation.

Neglecting to monitor critical metrics like open rates, bounce rates, and spam complaints is another pitfall. Without regular tracking, small issues can snowball into major problems before you even realize it.

Finally, failing to set up proper email authentication - such as SPF, DKIM, and DMARC - before starting the warm-up process can lead to deliverability issues right out of the gate. ISPs are much more likely to filter or block your emails if these protocols aren’t correctly configured.

Avoiding these mistakes lays the groundwork for a smoother and more effective warm-up process.

Best Practices for IP Warm-Up Success

To ensure a successful warm-up, follow these tried-and-true strategies:

Start with your most engaged recipients. Focus on contacts who have recently interacted with your emails. Positive engagement signals, like opens and clicks, help ISPs view your IP as trustworthy.
Stick to a consistent sending schedule. Whether you’re sending emails daily or weekly, maintaining predictability helps ISPs recognize legitimate behavior. Planning ahead also avoids sudden gaps or volume spikes.
Gradually increase your email volume. Begin with 50–100 emails per day in the first week, then slowly ramp up based on engagement metrics. Depending on your goals and list quality, the warm-up process typically takes 15 to 60 days.
Monitor performance daily. Aim for open rates above 20%, bounce rates below 2%, and complaint rates under 0.1%. Automated alerts can help you quickly address any spikes in bounces or complaints.
Segment your audience by engagement. Start with your most active contacts, then gradually expand to include moderately and less engaged recipients. This tiered approach ensures steady, positive engagement signals throughout the process.

For B2B campaigns, working with services like Artemis Leads can be a game-changer. They offer clean, verified prospect lists and combine personalized email outreach with LinkedIn messaging, helping you build a strong sender reputation while maintaining high engagement.

Manual vs. Automated Warm-Up: Pros and Cons

Deciding between a manual or automated warm-up approach depends on your team’s resources and the complexity of your campaign. Each option comes with its own benefits and challenges.

Method	Pros	Cons
Manual Warm-Up	Full control over recipient selection and timing; customizable pacing; granular segmentation	Time-consuming; prone to human error; requires expertise; challenging to scale
Automated Warm-Up	Streamlined process with minimal oversight; automatic volume adjustments; adherence to best practices	Limited flexibility; may not adapt perfectly to unique lists; potential additional costs

Manual warm-up is ideal for smaller campaigns where precision and control are key. However, it does demand significant time and expertise.

On the other hand, automated tools simplify the process, making them a great option for high-volume campaigns or teams with limited experience in email marketing. Many email service providers now offer built-in automation that adjusts sending volumes based on engagement metrics, reducing the risk of errors.

Ultimately, the choice between manual and automated warm-up depends on your team’s capacity and experience. Automated tools can provide a safety net for less experienced marketers, while manual approaches allow for greater customization and control in more complex campaigns.

Conclusion: Building a Strong Foundation for Cold Email Success

IP warm-up is the bedrock of any successful B2B cold email campaign. It’s the difference between your emails landing in inboxes or being flagged as spam. Establishing a solid sender reputation from the very beginning is crucial to avoid costly setbacks.

Start small and steady: send 50–100 emails per day, gradually increasing over a period of 15 to 60 days. Rushing this process can lead to blacklisting, which often requires months of recovery that could have been avoided with proper planning.

Don’t overlook technical details. Authentication protocols like SPF, DKIM, and DMARC are essential to prove the legitimacy of your emails. Without these in place, even the best warm-up strategy will struggle to achieve results.

Ongoing success hinges on consistent monitoring. Keep a close eye on open rates, bounce rates, and complaints. Combine this with rigorous list management and segment your audience based on engagement levels to maintain strong deliverability.

For B2B companies aiming to refine their outreach, services like Artemis Leads offer a comprehensive approach. They combine verified prospect lists with personalized email and LinkedIn outreach, ensuring high engagement while protecting your sender reputation. Their strategy focuses on quality and authenticity, as highlighted in their methodology:

"We make sure each interaction feels authentic and personal. Outreach comes from a real team member to boost trust and response rates. We use their LinkedIn and create matching email accounts." - Artemis Leads

Whether you opt for manual or automated warm-up techniques, the principles remain consistent: start small, increase gradually, monitor results, and prioritize quality over quantity. These steps lay the groundwork for a successful cold email strategy.

Think of IP warm-up as a long-term investment in your email marketing efforts. The time and effort you put into building a strong sender reputation will pay off with higher deliverability, better engagement, and more qualified leads for your sales team. By following these practices, you’ll set your campaigns up for measurable success and sustained growth.

FAQs

Why is email authentication important during the IP warm-up process?

Email authentication is a key factor in ensuring the success of your IP warm-up process. It confirms that your emails originate from a reliable source, reducing the chances of them being flagged as spam. By implementing protocols like SPF, DKIM, and DMARC, you can establish your domain’s credibility and improve the odds of your messages landing in recipients’ inboxes rather than their spam folders.

These authentication measures also help build trust with email service providers (ESPs) - a critical step when you're gradually increasing your email volume during the warm-up phase. Without proper authentication, your emails are more likely to be blocked or marked as suspicious, which can hurt both your deliverability rates and the overall success of your campaigns.

What are the risks of using purchased email lists during IP warm-up?

Using purchased email lists during the IP warm-up phase can seriously damage your email deliverability. Why? These lists often include outdated or invalid email addresses, leading to high bounce rates that hurt your sender reputation. Plus, many of these recipients never agreed to receive your emails, which means you're more likely to face spam complaints.

To get the best results during IP warm-up, stick to a clean, permission-based email list. Send emails to people who want to hear from you - this helps build trust and keeps your sender reputation intact.

How can I monitor and improve my IP reputation to ensure better email deliverability?

To keep your IP reputation in good standing, start with a gradual warm-up strategy. This involves slowly increasing the volume of emails you send over time, which helps build trust with email providers and reduces the risk of being flagged as spam.

Using monitoring tools is another critical step. These tools allow you to keep an eye on your IP reputation and spot potential problems, like high bounce rates or frequent spam complaints. The key to maintaining a solid reputation is consistently sending high-quality, relevant emails to verified recipients.

For businesses looking to take their outreach to the next level, partnering with experts like Artemis Leads can make a difference. They specialize in connecting companies with decision-makers through tailored email and LinkedIn outreach, helping you reach your target audience while safeguarding your sender reputation.