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Did you know that over 20% of cold emails never make it past spam filters?
For businesses relying on email outreach, this means missed opportunities and wasted effort.
But there’s a solution: warming up your email before launching a cold outreach campaign.

Cold email warm-up is a process that gradually builds your email account’s reputation, ensuring your messages are trusted by Email Service Providers (ESPs). It’s not just about avoiding spam—it’s about maximizing deliverability, engagement, and campaign success.

In this guide, we’ll cover everything you need to know about warming up your email, from authentication protocols to strategic sending practices. Whether you're new to cold outreach or a seasoned pro, these tips will help you master the art of email warm-up and reach your audience effectively.

Before diving into the step-by-step guide, here are some quick, expert-backed tips to help you successfully warm up your email address and domain:

Start with 5-10 emails daily; increase volume gradually to avoid ESP red flags.
Set reply rates at 30-35% for realistic engagement.
Use read emulation to mimic human behavior, boosting credibility.
Avoid links in signatures during the warm-up phase.
Configure custom tracking domains for better deliverability.
Group accounts with descriptive tags for easier management.
Monitor open rates and adjust settings if performance drops.
Limit new domains to 1-2 accounts initially to build reputation steadily.

Warming Up Email - A Brief Overview

Cold email warm-up involves gradually building trust and engagement with your audience before sending large-scale campaigns. This method ensures higher deliverability, better engagement rates, and a stronger sender reputation. Here’s how it works:

Start by engaging with prospects through other channels like LinkedIn or social media.
Slowly send emails to a smaller audience to build positive interaction metrics.
Gradually scale your email campaign once ESPs recognize your domain as trustworthy.

How to Warm Up a Cold email list (Step by Step)

Warming up cold contacts is a crucial step in establishing a successful email outreach campaign. By employing effective techniques, you can enhance your email deliverability and improve engagement rates with your audience. This process involves building a positive reputation with email service providers (ESPs) and ensuring that your emails reach the intended recipients without being flagged as spam.
Here are some effective techniques to help you warm up your cold contacts:

1. Authenticate Your Email Account

Making sure your email account is authenticated before sending cold emails is super important. This process checks that the emails you send are really coming from you. It tells email providers that your messages are not spam, enhances your reputation, and improves your email deliverability.

Authentication involves setting up a trio of protocols: SPF, DKIM, and DMARC.
So, What is the protocols?

SPF (Sender Policy Framework) helps you specify which servers can send emails from your domain.
DKIM (DomainKeys Identified Mail) adds a digital signature to ensure emails haven't been tampered with before reaching the recipient.
DMARC (Domain-based Message Authentication, Reporting & Conformance) combines SPF and DKIM to verify emails and provides guidelines for dealing with failed verifications.

This Video will help you to understand more about the terms SPF, DKIM & DMARC and also how to set it up.

Tip: Edit your domain’s DNS settings to set up these protocols and use testing tools to verify the configuration.

Setting up SPF, DKIM, and DMARC requires editing your domain's DNS settings. Once you've updated the DNS settings, there are many tools available to test if SPF, DKIM, and DMARC are configured properly.

2. Use a Custom Domain

A custom domain is an email address that uses your business’s domain name instead of a generic email provider. You can buy these from which providers you are comfortable.

For example, instead of using something like yourname@gmail.com, you would use yourname@yourcompany.com.

Using a custom domain for Email Marketing Campaign

Attention: Make Sure, You are using 3-5 Business mail from a Domain for outreach. For a new domain, use 2-3 mail addresses. David Chastanet (email deliverability expert) says that using more than 3-5 email addresses from a single domain will ruin any campaign.

This makes your emails look more professional and trustworthy. Plus, a custom domain allows for better tracking and analysis of your cold campaign performance.

3. Send Initial Emails to Warm Contacts

This step involves reaching out first to people who already know you or your business. These could be existing customers, partners, colleagues, or family members.

Warm Contacts through emails that increase sender reputation

ESPs track how recipients interact with your emails.

Here, Thomas engaged his audience by providing free resource which people wants most.
Some benefits are:
1. You can segment audience by tracking links
2. Your Email Open rate will high, that will help to increase authentication rate.
3. By getting segmented audience list, you can run Ads to offer your desired service/products.

Compared to low-engagement emails, those with high engagement have a 440% better chance of reaching the inbox according to hubspot research.

However, known contacts are more likely to open and engage with your emails because they recognize your name or brand.

This initial engagement helps establish a positive sending reputation for your email account. If ESPs see high open rates and low bounce rates from your warm contacts, they are more likely to deliver your future emails.

4. Target the Right Prospects

When you send relevant messages to people who genuinely need your product or service, they're more likely to engage with your emails.

This engagement signals to email providers that your address is legitimate and used for genuine communication. Plus, targeting the right prospects ultimately leads to successful cold email outreach which converts those cold contacts into warm leads.

So keep your mind to follow these:

Research your ideal customer profile (ICP).

Understand their industry, company size, demographics, and specific challenges that your product or service can address.
Search on LinkedIn or contact databases that fit your ICP to find potential leads.
Segment your prospects into different groups based on factors like industry, company size, job role, or specific needs.
Make sure the list is clean and up-to-date.

Explore More: LinkedIn Cold Outreach 2025: 30+ Templates, Strategy and Trends

5. Validate Your Email List

Validating prospect email addresses before a cold email campaign is crucial for maximizing its effectiveness. It involves checking the accuracy and validity of email addresses in your contact list.

A clean email list ensures high deliverability. Use verification tools to remove:

Invalid or outdated email addresses.
High-risk addresses that may result in bounces.

At its core, verification tools check if an email address exists and can receive emails. Then they remove invalid or outdated email addresses from your list. This process significantly reduces bounces, which can negatively impact your sender's reputation and lead to emails being flagged as spam.

Pro Tip: Regular list validation minimizes bounce rates and protects your sender's reputation.

6. Gradually Increase The Send Volume

Email service providers monitor sending behavior.
A sudden spike in outgoing emails from a new account appears suspicious and spammy to ESPs.

They might flag your emails and send them straight to recipients' spam folders. So, don't send emails to your entire list at once. Start with a smaller and targeted segment.
A common tactic is to send a modest 10-20 emails per day from a new account and then slowly raise the sending volume.

Pro Tip: Monitor your engagement rates and adjust the sending frequency as your reputation improves.

As you gradually increase the volume over days or weeks, you give ESPs time to recognize your sending pattern as legitimate and non-spammy.

Using ai tools: How to warm up your Domain for Cold Email

AI tools simplify and optimize the process of warming up your email accounts, ensuring higher deliverability and engagement rates. One of the most user-friendly options for me that I've used and suggested to Hundreds of agency owners in the past 3 years is Instantly AI, which automates the warm-up process with minimal effort. Here’s how to get started:

1. Set Up Your Email Account

Log into Instantly AI and navigate to the Email Accounts section.
Click on “Add New” to integrate your email account. Simply follow the on-screen instructions to log in securely.

2. Enable Warm-Up Mode

Once your account is set up, toggle the Warm-Up option to activate it for the selected email address.
Customize settings to align with your campaign goals and to mimic natural sending behavior.

3. Configure Warm-Up Settings

Take the time to fine-tune these key settings:

Daily Sending Limit: Start with 5-10 emails per day and gradually increase by one email daily to avoid triggering spam filters.
Reply Rate: Set an appropriate reply rate (e.g., 30-35%) to emulate real conversations.
Read Emulation: Enable this option to have AI tools open and scroll through your emails, making it appear as if they were read by humans.
Wait Times: Space out email sends by at least 15-20 minutes to simulate organic activity.

4. Use Custom Tracking Domains

Enhance deliverability by setting up a custom tracking domain through your hosting provider.
Follow the detailed guide within Instantly AI’s help section to configure CNAME records effectively.

5. Automate the Warm-Up Process

Instantly AI uses tags and automated processes to self-send emails between accounts, open them, and even mark them as important. This consistent interaction builds a strong sender reputation without manual effort.

6. Monitor Performance

Track engagement metrics such as open rates, reply rates, and spam placements directly from the Instantly AI dashboard.
Adjust your settings as needed to refine the process and maximize deliverability.

Why Use AI for Email Warm-Up?

AI-driven tools like Instantly AI not only save time but also ensure precision in warming up your domain. By mimicking human-like email activity, they help establish trust with Email Service Providers (ESPs), making your outreach campaigns more effective.

Key Takeaways

Build trust with email providers: Sending a burst of emails from a new account looks suspicious. Take it slow. Gradually increase the number of emails you send to build a good reputation.
Start with people who know you: Reach out to existing customers, colleagues, or friends first. They're more likely to open your emails, which helps establish you as a legitimate sender.
Use a professional email address: A custom domain email address looks more trustworthy than a generic email address.
Target the right audience: Send relevant emails to people who might be interested in your product or service. This shows email providers you're not a spammer.
Clean your list: Using an email verification tool, get rid of any invalid or outdated email addresses to avoid bounces, which can hurt your sender's reputation.

Next Steps

While the strategies above provide a solid foundation for warming up cold contacts, consider using a CRM platform to streamline and enhance your cold email outreach efforts.

Centralized Platform: Manage all your cold outreach activities, contact information, and campaign performance data within a single, unified platform.
Segmentation and Targeting: Easily segment your contact list based on various criteria, which allows you to target highly relevant prospects with personalized messages.
Email Automation: Automate repetitive tasks like sending follow-up emails, scheduling emails, and managing bounces. This saves you a lot of time and effort.
Advanced Analytics: Gain valuable insights into your cold email campaigns' performance, including open rates, click-through rates, and replies. This data helps you refine your approach and improve results over time.
Integration with Marketing and Sales Tools: A CRM also offers marketing, sales, and customer service tools. This alignment streamlines workflows and enhances productivity.

Doplac is a one-stop shop for business management tools. This means no more switching between different platforms or wasting time searching for specific tools. One subscription grants you access to all the features, saving you time and streamlining your tasks.

Warm Up Emails Like a Pro: Guide to Boost Inbox Deliverability in 2025