Warming up your email account before you send your cold email campaigns is one of the best ways to ensure your emails land in your recipients’ primary inbox.

There are a variety of dedicated cold email warmup tools that will generate positive engagement on your email account, so you’re probably wondering: do they work, and what’s the difference between all of them?

In this guide, I’ll explain how these warmup tools work, and show you some of the best tools on the market, including a completely free option, Mailflow.

  1. Warming Up Your Email Address: Automated vs Manual Methods

  2. The 13 Best Cold Email Warm Up Tools In 2024

  3. Features to Look for in Your Email Warm Up Tool

  4. Other Factors That Can Affect Your Email Warm Up Strategy

  5. Finding the Best Solution for Your Business

Let's dive straight in.

Warming Up Your Email Address: Automated vs Manual Methods

There are two main ways to warm up your email inbox.

The first method is to run the process manually. After setting up your new inbox, you’ll send emails to your coworkers, sign up to newsletters, reply to incoming emails, and generate completely natural engagement signals on your inbox.

You’ll slowly ramp up your email sending volume and over time, the main email providers like Outlook and Gmail will trust your account.

The second method is by using an email warm up tool, like the MailFlow Auto Warmer.

These tools help you automate the email warm up process by generating real daily activity on your inbox. 

Every day, they’ll send a low-volume of emails to other users in their email warm up network, showing email service providers that you’re a trustworthy user and helping you improve your email deliverability.

The 13 Best Cold Email Warm Up Tools in 2024

1. Mailflow: Free, And Does It All

Before Mailflow, you could easily spend thousands of dollars per month just to warm up your email addresses.

With Mailflow, you can now warm up to 100 inboxes completely free. And it's not just the pricing that makes this tool great. After testing many warmup tools, Mailflow stood out as one of the best in terms of quality and features.

Let's dive into why Mailflow is the #1 email warmup tool out there.

Generate Real Engagement to Warm Up Your Email Address

Once you’ve linked your email account with Mailflow, your email address will automatically start sending and receiving emails to and from other real people using Mailflow.

You’ll choose how many emails you want to send per day, and the process will start.

When a Mailflow email is sent from your address, it will be automatically opened and replied to, in the same way a real email to a friend or coworker would be engaged with.

If your emails ever get caught in the filter, they’ll be automatically marked as ‘not spam’ and moved to the primary inbox to reduce the chances of it happening again.

With time, you’ll be showing ESPs that you’re a trustworthy sender that sends and receives real emails, making them less likely to flag you as a spammer when you launch your email campaigns.

Mailflow emails are automatically removed from your primary inbox after being sent or received, so your inbox will stay organized throughout the process.

Get Accurate Reports on Your Inbox Deliverability Performance

You’ll see detailed reports into your inbox performance: how often you’re landing in the main inbox, the spam folder, or other folders like the Gmail Promotions tab.

When you see that your email domain is performing well and your daily emails are regularly landing in the main inbox, you know you’re ready to start sending your first cold email campaign.

You can also see how your emails are being received by the main inbox and email providers, including free Gmail, G Suite, free Outlook, and Office 365.

If you ever see emails being delivered to spam, you can take steps to solve the problem and ensure future campaigns get delivered to the main inbox.

Send Untraceable Emails

Artificial intelligence ESP filters are getting smarter every day. Unusual inbox activity is ever more likely to be noticed, so you need to ensure your warmup platform isn’t going to cause more harm than good.

One factor that filters look for is the language you use in your emails. If the emails from your email warmup tool deviate from regular business language, that can get you penalized.

Some warmup tools send email templates talking about animals, plants, and other random topics just to fill the word count. Mailflow emails use real business language that will blend in with your other emails and be undetectable by smart spam filters.

Another risk factor is the code attached to the emails by some tools for tracking purposes. Mailflow emails have a very low code footprint, making them very similar to emails sent manually from your own inbox.

Take Your Deliverability to the Next Level

If you want to go the extra mile when it comes to email deliverability, Mailflow offers a broader set of features designed to help you monitor and further improve it.

On Mailflow's paid plans you can get access to SPF & DKIM configuration assistance, blacklist monitoring on up to 100 blacklists for all your domains, and a daily sender reputation tracker with various providers to help you decide whether to continue or slow down some of your email activity.

Another upcoming feature is a redirection & uptime monitor to make sure your cold outreach domains lead to a valid web page. The monitor will notify you if a page is broken so you can fix it immediately.

These tools go beyond email warmup and are created for those who want to scale their email outreach while continuing to have great deliverability.

Native Integration with a Powerful Cold Email Automation Platform

QuickMail is a powerful platform for sending cold emails and LinkedIn outreach. 

You can upload your sales prospects, craft personalized templates, and schedule your emails and follow-ups to send and land in your prospects’ inbox at the perfect time.

a follow up campaign in quickmail showing email and linkedin steps

Mailflow is natively integrated into QuickMail so that you can see your Mailflow sender reputation score from your QuickMail dashboard.

As you increase the volume of emails you’re sending every day, you can regularly review your Mailflow sender reputation scores to ensure your emails are still being sent to your prospects’ main inbox and that you're maximizing the opportunities from every outreach campaign you send.

Who is it for: Small and medium businesses, agencies, and anyone wanting to use cold outreach to grow

Pricing: Generous plans from $49 per month 

What users are saying:

  • "What they provide is hands down the best experience I have had as a customer. Being in sales I have high expectations because I deliver a great customer experience."

  • “The ultimate email auto-warmer solution - free for as many inboxes as you need”

  • “We love the built-in warmup features and all the integration capabilities.”

Best Features:

  • Powerful free tool to warm up your email address

  • Designed specifically for cold emailers

  • Engagement group made up of real people and real email addresses

  • Warm up additional team inboxes for free

  • Detailed deliverability reports to see where your emails are landing

2. Warmup Inbox: Good Solution, But It Comes At A Price

Warmup Inbox is a standalone email warming software.

They use a network of real inboxes, and once you sign up, your account will start engaging with these other accounts using Warmup Inbox.

It works with all of the main email service providers, including Gmail and Outlook 365, as well as Yahoo Mail, Amazon SES, and other custom inboxes.

You can send 1,500 emails per month per inbox on the base pricing plan, and they recommend that you use the service for at least 45-90 days to fully warm up your inbox before sending any sales email campaigns.

Best for: Email marketers needing a standalone email warmup service

Pricing: Starts at $12 per month per inbox for 50 emails per day. $39 per inbox per month for 150 emails per day. $199 per inbox per month for 500 emails per day.


  • A clear overview of whether your inbox is ready with a ‘health score’

  • Email blacklist monitoring to see if email providers trust your inbox and sender reputation

  • Good range of features considering it’s more affordable than most other email warmup tools options in this guide


  • Capterra users report that it can take months to see deliverability improvements

  • Gets expensive if you need to warm up multiple cold email inboxes

  • Not part of a cold email platform ecosystem, so it’s an extra cost

3. Warmbox: If Pretty UI Is Your Thing

Warmbox is a standalone email warming tool with great UX & UI design.

It has all the basic ingredients of a good email warm up tool: integration with the main email service providers, a large network of inboxes, and clear deliverability reporting so you know where your emails are landing.

Best for: Individuals or teams doing regular cold outreach

Pricing: Starts at $15 per month for 1 inbox, $69 per month for 3, $139 per month for 6. Unfortunately, there are no discounts for adding more inboxes.


  • Ongoing spam score monitoring to flag any potential issues

  • Choose from different email sending schedules to reflect real usage

  • Works with a variety of inbox providers so probably compatible with the one your company uses

  • Clear email deliverability rate reports you know when your inbox is warmed up


4. Mailwarm: An Expensive Alternative

Mailwarm’s team has set up thousands of email accounts that your inbox will interact with on a schedule that you set. There’s no indication that the inboxes your emails will be sent to are real people’s inboxes, which could be a downside if ESPs look critically at your email activity.

Once you connect your email account, you can set your email warm up schedule, and Mailwarm will start sending and replying to emails for you, warming up your account over time.

Best for: Anyone sending a cold email outreach campaign that wants to avoid the spam folder

Pricing: $828 per year, or $79 per month per inbox (billed monthly). $159 per month for up to three accounts. One of the most expensive email warming tools in this guide.


  • Engage with a network of Mailwarm’s own email addresses

  • Set your own sending and reply schedule

  • If you’re technical it’s easy to use, as it’s installed via a SMTP setup


  • Only works with SMTP setup, so it can be tricky to set up if you haven’t set inboxes up that way before

  • Users on Capterra struggle to integrate it properly with Gmail

  • Expensive option at $79 per inbox

5. WarmUpYourEmail: A Human Touch?

WarmUpYourEmail is a cold email marketing inbox warming service that uses a real team to generate engagement with your emails.

Their team engages with your emails by opening them, replying to them, marking them as important, and removing them from the spam folder (if your emails land there).

It’s worth noting that there are no clear details on how their team manages to do this, and we’d recommend contacting WarmUpYourEmail if you have questions about the process.

Best for: Anyone needing a simple inbox warm up service before sending bulk emails to cold prospects or in a marketing campaign

Pricing: $29/month per inbox, for 50 emails per day on one account. $49 per month for 50 emails per day on three email accounts.


  • Real people opening, replying, and engaging with your emails

  • Helpful free tools to review your DMARC, SPF, SMTP

  • Works with all major inbox providers


  • No information on how their email warm up service runs in the background

  • Becomes expensive if you want to send more than the base number of emails per day

6. lemwarm: Used To Be Popular

Lemlist were the first to come to market with an email warmup tool (lemwarm). They deserve recognition for that, which is why we included them here.

Lemwarm is a simple and straightforward cold email warm up tool that also connects to their email platform.

With Lemwarm, you can decide how many emails per day you want to send, and the tool will start automatically sending and replying to emails, just like the other tools on our list.

Best for: Anyone wanting to improve their email deliverability.

Pricing: $29/month per inbox.


  • Choose how many emails you send per day

  • Automatically increase the volume of emails sent

  • One of the first to market, so they know the importance of email warmup


  • Relies on templates with unnatural email copy which can still be suspicious to inbox providers

  • Mid-to-high price range and not included in the standard plan by default

  • Can have issues with reliability, and users report that Lemwarm sometimes pauses without warning.

7. Mailreach: Good for a Small Number of Inboxes

Mailreach is an easy-to-use email warm up platform to help you improve your deliverability.

Once you’ve connected your inbox, Mailreach will run on a fully automated schedule.

It includes inbox deliverability reports, email blacklist, DNS checks, as well as a smart warming algorithm to adjust the process continuously to get the best results.

Best for: Anyone needing a standalone email warmup tool

Pricing: $25 per inbox month for between one and five inboxes. For more than that, pricing lowers to $19.50 per inbox per month.


  • Works with Gmail, Outlook, and other third-party inbox providers

  • Fully automated, so you only need to check back semi-regularly to verify it’s performing as expected

  • Easy-to-understand dashboard that lets you monitor email warm up performance


  • Reviews on Capterra say it’s hard to warm up multiple email inboxes at once

  • Not connected to an email outreach tool so you’ll need to subscribe to one separately

8. Folderly: AI-Based Email Warmup?

Folderly is aimed at large companies and it comes with a variety of helpful deliverability features. For example, there’s a basic email warm up tool that gets any account ready for basic outreach, then, an upgraded version for teams expecting to run high volume outreach that includes email content analysis and more powerful tools to diagnose potential issues.

Best for: Large teams with a budget who want an effective and quick way to warm up email addresses

Pricing: Starts at $49 per month for the basic warmup plan. $200 per month for specific cold outreach warm up features. $129 per month for email deliverability tests. The most expensive solution in this guide.


  • Email content analysis that will suggest improvements to copy based on how well it expects emails to be delivered

  • Email deliverability audit to identify causes of poor deliverability


  • Users say that the documentation is difficult to understand and the tool takes a while to set up correctly

  • No email outreach features included, so you’ll need to use a separate tool like QuickMail

9. Warmy: If Your Focus is Email Marketing

Warmy is made for teams with multiple email marketing inboxes that need warming up.

The tool uses an AI-based algorithm to automate the process of sending, receiving, and replying to emails from your inboxes to signal positive engagement and you can track how warmed up your inboxes are in visual dashboards.

Best for: Teams running bulk marketing email campaigns that need to warm up their inboxes.

Pricing: $49 per month for one inbox and 100 emails per day. $129 per month for three inboxes and 300 emails per day.


  • AI-based sending tools to quickly warm up your inbox

  • Deliverability checker that compares performance across the major inbox providers

  • Good customer support if you have issues


  • Lack of pre-made warm up templates so you need to create them yourself

  • Expensive compared to other options in this guide

10. Mailivery: Too Early to Try?

Once you add your cold email inbox in Mailivery, the tool will send warm up emails on a schedule that you set. The schedule lets you mimic natural, human-like email patterns and lets you skip nights or weekends, for example.

It integrates with all major inbox providers, and it’s quick to get up and running with.

Best for: Sales teams wanting a quick way to improve deliverability for their cold emails

Pricing: $35 per inbox per month, which includes 35 warm up emails per day. $65 per inbox per month for 65 warm up emails per day.


  • Works with Gmail, Outlook, and custom inbox providers

  • Uses a peer-to-peer network of real inboxes, similar to MailFlow's Auto Warmer, for the most natural warm up pattern


  • Expensive considering the number of warm up emails per day is relatively low on the most affordable pricing plan

  • Users on Capterra say that there are no notifications if there are deliverability issues which could be harming your inbox in the background

  • Some customers report that there can be downtime for periods of up to 7 days without being notified of it

11. Klenty: Email Warm Up Add-On

Klenty is a sales engagement platform made for people running multichannel outreach, including cold email. The company released an email warmup tool as an optional add-on to help users improve their email deliverability.

The warmup service sends emails at random times to generate natural activity on your account and provides reports showing you how many of your mails are landing in the primary inbox or in other inbox folders.

Best for: Those looking for a simple email warm up platform

Pricing: From $240 per year per inbox being warmed up. It’s an additional cost on top of your standard Klenty account, which starts at $50 per user per month.


  • As well as an email warming service, there’s a spam checker and email template review tool to help improve your cold outreach process

  • Clear reports on where your emails are landing: primary inbox, promotions, or spam


  • Expensive option because email warming isn’t included in the main Klenty pricing plans

12. Reply: Expensive for Multiple Inboxes

Reply is a sales outreach platform that includes cold email tools to help you reach out to prospects. The company offers an extra email warm up tool for Google Workspace and Outlook to improve deliverability and help you land in the primary inbox.

Best for: Enterprise sales teams using Reply that want to quickly improve their domain reputation and warm up their inboxes.

Pricing: $29 per inbox per month. Included on the Professional plan for $90 per user per month, but optional extra on the Starter plan at $60 per user per month


  • If you’re already using Reply, it makes sense to use the add-on to easily connect your inboxes

  • Clear reports to show you where your emails are landing during the warm-up process

  • Uses a network of real inboxes rather than generating their own fake inboxes so it will be more natural


  • Not included in Reply’s Starter plan, so you’ll need to pay extra to use the email warming features

13. InboxWarm: In Case None of the Other Options Work for You 

InboxWarm is ideal if you already use OutreachBin’s email tools.

Like most of the other tools we’ve looked at, it works by adding your email domain to a peer to peer network of other inboxes using the service.

Once you select the number of warmup emails to send per day, it will automatically start sending emails between the inboxes to naturally warm up your cold email inbox. 

Pricing: From $19.97 per month per inbox


  • Peer-to-peer network of inboxes to mimic real activity

  • Good for existing users of OutreachBin’s email tools


  • No automatic SPF and DKIM checks

  • Expensive for teams, as you need to pay for every inbox you add

Features to Look for in Your Email Warm Up Tool

All of the email warmup tools we’ve looked at have similar features, as they’re all designed to help you achieve the same outcome: have more emails land in the primary inbox.

However, here are some key features to look out for:

1. Network of real inboxes: If you’re using fake inboxes to generate engagement, email service providers will notice. Look for platforms that use a network of real email inboxes for the warm up process. Your email inbox will be sending and receiving emails from real people, which is less likely to raise suspicions from platforms like Gmail and Outlook.

2. SPF and DKIM checks: Without SPF and DKIM records correctly implemented on your inbox, your emails are guaranteed to land in the spam folder. Some tools like Mailflow have built-in SPF and DKIM checks that run automatically and notify you if there are issues so you can quickly fix them.

3. Sender reputation monitoring: A good sender reputation ensures your emails are consistently inboxed by the main email service providers. Your sender reputation is an invisible score given to your inbox by ESPs affected by factors like your IP reputation, the content of your emails, the engagement levels, and more. Having an email warming service that helps you understand your sender reputation ensures you can avoid running campaigns when your sender reputation is low, and spend more time on your warm up process.

4. Multi-inbox compatibility: If you have a growing team or run an agency, you’ll need to send emails from multiple inboxes at once. Look for cold email warm up software that allows you to add multiple team inboxes and monitor their deliverability rates all in one place. This will save you countless hours of logging in and out of different accounts and streamline your process for tracking inbox email deliverability.

5. Warm up emails with natural-sounding copy: Email service providers look at hundreds of signals to determine your email deliverability rates. Part of that is your email copy. Look for a platform that uses real, business-like language in their email warm up templates. This ensures ESPs see you’re being consistent with your messaging. Some email warming platforms use completely AI-generated sentences that are out of context for what your inbox would send, which could be a risk factor.

Mailflow includes all of these and more, and it’s free to get started. Plus, there’s a native integration with QuickMail, making it easy for you to check your deliverability before launching a cold outreach campaign.

Other Factors That Can Affect Your Email Warm Up Strategy

1. The Longer You’ve Owned Your Email Address, The Better

If you buy a brand new domain from Google Domains or Namecheap and start using it to send emails, email service providers won’t trust you. You need to establish your domain reputation, so warming up a new email address is vital if you want your cold emails to land in your recipients’ primary inbox.

To build trust with the major email providers, you’ll need to grow your email activity over time. 

Another shortcut to building trust with Google in particular is to pay for six months of your G Suite subscription in advance. We talk more about this strategy here, but the premise is simple: Google is less likely to restrict a customer that is willing to pay for the service.

2. The Quality of Your Email List Matters

No matter how long you warm up your email, everything will come crashing down if you send 1,000 emails to people who aren’t interested in your product or services and don’t want to hear from you.

Worse, you might be sending emails to invalid email addresses and they’ll be instantly rejected.

To avoid this, first, spend time building your email list. Make sure every person you reach out to is highly relevant to what you’re offering.

Then, use email verification tools like Dropcontact and NeverBounce to verify the email addresses in your prospect list are valid. You’ll show email service providers that you’re not just spamming every email address you can find, but instead, are sending targeted, personalized emails that your recipients will want to read.

3. The Level of Personalization in Your Outreach Emails Affects Deliverability

Finally, one of the most important lessons: always personalize your email outreach.

Every email you send should have unique personalization, such as your prospect’s:

This is going to help you get more replies to your outbound email campaigns, as well as being a positive signal to email service providers. They’ll know you’re not copy-pasting your template and are sending real, high-quality emails with a unique message for each recipient.

In QuickMail, you can use Attributes to personalize your outreach, even at a high volume of sends.

For example, you can use any information you know about a lead, or create computed attributes to suggest unique meeting times at scale.

When someone receives your personalized email, they’ll know you’ve spent time researching them and will be more willing to have a conversation with you.

4. Your Inbox’s Technical Setup

The email warmup process won’t make a difference if your inbox doesn’t have the technical fundamentals in place.

When we say this, we’re talking about:

  • Sender Policy Framework SPF records: This record shows ESPs that you’re a legitimate sender and reduces the chance of inboxes blocking your emails.

  • DomainKeys Identified Mail (DKIM) records: DKIM is an authentication protocol that shows ESPs that you are who you say you are, and your email isn’t being spoofed by a spammer.

  • Domain-based Message Authentication, Reporting & Conformance (DMARC): DMARC is effectively an instruction to email servers on how to handle emails from your domain: do nothing, quarantine the email, or reject it completely.

Having these three records correctly implemented will massively boost your chance of landing in the primary inbox vs. the spam folder.

5. The Total Email Send Volume Per Inbox

Another important factor to consider is the number of sent emails per inbox.

If you’re only relying on one cold email inbox, ESPs will notice that you’re sending an unusually high amount of emails and may start to throttle your emails and send a higher percentage of them to the spam folder.

The best way around this is to use a cold email tool that allows you to add multiple cold email inboxes and use inbox rotation to spread your sending volume between them.

You can do this in QuickMail’s free plan, so there’s no reason not to.

Once your cold email campaign is ready, you’ll select the inbox you want to send a campaign from. Rather than choosing one, you can select multiple.

Your emails will be sent across multiple inboxes, which ensures you’ll never exceed your sending limits and have any inbox risk getting caught in the spam filter unnecessarily.


Finding the Best Solution for Your Business

If you want to get started with a powerful and cost-effective tool, use Mailflow. It’s completely free for QuickMail users, and within 1-2 weeks your sender reputation will be improving. There’s a native integration with QuickMail’s cold email platform, so it’s quick to go between the two to review your deliverability stats.

QuickMail has a Gmail-approved sending API for better deliverability. Paired with Mailflow's warmup it's a powerful growth engine.

Leave it running in the background, even after you’ve started to send your campaigns, and you’ll be confident knowing that your emails are always going to be seen by your prospects.

However, it’s key to remember that these warm-up tools won’t solve every problem for you. You still need to invest in creating a high-quality prospect list, writing personalized and unique emails, and having a value proposition that the people you’re reaching out to care about, and are willing to engage with you to learn more about.