Updated September 28, 2026 | 18 min read

We Tested 11 Best Email Warmup Tools: Here's the One That Won Each Category (2026)

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Eleven warmup tools. Three weeks. Fresh inboxes on Gmail, Outlook, and a custom SMTP domain, all sending into the void so you don’t have to burn your own domain learning the same lesson. Here’s what nobody says out loud: almost every tool on this list will lift your sender reputation if you leave it running long enough. The differences show up later, on the Tuesday morning when half your sequence lands in spam and you need to know which provider flagged you and why.
That’s the gap I set out to measure. In this post, I’ll show you which tool won each category, how the peer networks actually behave once you connect a fresh inbox, what pricing model makes sense for one mailbox versus fifty, and the mistakes that quietly undo three weeks of warmup. lemlist makes one of the tools in this roundup, so treat my bias as declared and judge the rest on the testing.

Best email warmup tools at a glance

Warmup tools do the same core job. They raise sending volume slowly from a new or dormant account and generate engagement that inbox providers read as legitimate. What separates them is the network behind the sends, how much of the result they show you, and how the bill scales when you add mailboxes.
Here’s the whole field in one table, with the use case each tool won during testing.
Tool
Best for
Pricing model
Skip it if
lemwarm
Native warmup inside your cold email sequences
Included with every lemlist seat
You don’t run outreach from lemlist
Mailreach
Detailed deliverability diagnostics per provider
Standalone subscription, priced per mailbox
You want warmup you never look at
Instantly Warmup
High-volume senders who need a large peer network
Bundled into the platform subscription
You send from a different outreach tool
Smartlead Warmup
Agencies running many client domains
Bundled, unlimited mailbox warming
You only have one or two inboxes
Warmforge
Hands-off setup, including authentication records
Paid plans with setup handled for you
You already configured DNS yourself
Mailwarm
Plain warmup with volume controls per provider
Standalone per-inbox subscription
You need spam placement reporting
Warmbox
Solo senders warming one or two inboxes
Standalone per-inbox subscription, low entry tier
You need advanced features at the cheapest tier
Warmup Inbox
Teams sharing visibility across SDR mailboxes
Standalone per-inbox plans with team access
You’re a team of one
Folderly
Enterprise deliverability audits and consulting
Highest price of the group, closer to a service than a tool
Warmup is all you need
TrulyInbox
Small teams on the tightest budget
Lowest per-inbox price I found
Reporting depth matters to you
InboxAlly
Repairing placement after warmup didn’t fix it
Standalone subscription, separate from any outreach tool
You’re starting from a brand new domain
Most of these vendors run a free trial or a limited free tier, so you can connect one mailbox and watch a week of sends before paying. lemlist’s is 14 days with no credit card, and lemwarm is part of it.

How we tested every email warmup tool

I ran each tool for three weeks on fresh inboxes before measuring anything, because a warmup tool judged after five days tells you nothing except that it turned on. Every tool got connected to Gmail, Outlook, and at least one custom SMTP domain, so I could see whether performance held up outside Google.
What I tracked:
  • How many warmup emails reached the primary tab instead of spam or promotions.
  • How fast the tool raised daily volume, and whether I could override its ramp when I wanted to go slower.
  • Whether warmup emails were exchanged with real business inboxes or with throwaway accounts spun up to pad a network.
  • Whether the reporting told me something I could act on.
  • Whether Gmail, Outlook, and custom domains got equal treatment, or whether the tool was really a Gmail tool wearing a coat.

What the three weeks actually showed

Directionally, every tool in the test improved primary-tab placement on the Gmail inboxes by the end of week three. That’s the boring headline, and it’s the one most roundups bury.
The spread appeared in two places. First, Outlook and custom SMTP lagged Gmail across the board, and the tools with provider matching closed that gap faster than the ones sending everything through a single pool. Second, reporting quality varied wildly. Some tools showed placement per provider, per day, with the exact messages that got filtered. Others showed a green checkmark and a progress bar, which is comforting and useless when you’re trying to work out why Outlook stopped trusting you.

The 11 best email warmup tools we tested

1. lemwarm

lemwarm runs inside lemlist’s Deliverability Hub, so warmup and outreach share one dashboard and one set of numbers. You can see which emails landed in spam and on which provider, which is more visibility than most standalone tools hand over.
The behavior I liked most: lemwarm adjusts around your campaigns instead of competing with them, so you don’t get the volume spike that happens when warmup and outreach fire from the same inbox on the same morning. The peer network exchanges mail with real lemlist users rather than manufactured accounts, and that shows up in cleaner engagement signals.
On pricing, lemwarm is included with every lemlist seat at no extra cost, so there’s no second invoice and no second login. lemlist holds a 4.6/5 rating on G2 across more than 2,000 reviews, which is the closest thing to a second opinion I can offer you here.
lemwarm dashboard inside lemlist's Deliverability Hub showing inbox placement by provider
What we liked
  • Placement data broken down by provider, in the same tool that sends the campaign.
  • Warmup that reacts to your sending volume instead of ignoring it.
What we didn’t
  • It only makes sense if lemlist is your outreach platform.

2. Mailreach

Mailreach produced the most detailed deliverability reports in the test. Spam placement breaks down by provider, so you can see Gmail flagging you while Outlook waves everything through, which is a distinction that changes what you do next.
It also watches blacklists and alerts you if your domain shows up on one. For a team trying to diagnose a drop rather than build reputation from zero, that granularity beats raw warmup volume.
Pricing is a standalone subscription charged per mailbox, so the cost scales in a straight line with your number of senders.
What we liked
  • The clearest per-provider spam reporting of any standalone tool.
  • Blacklist monitoring included rather than sold separately.
What we didn’t
  • Per-mailbox pricing gets expensive once an agency adds client domains.

3. Warmforge

Warmforge handles the technical setup most people either skip or get wrong. The service configures SPF, DKIM, and DMARC for you, then tunes warmup speed based on how inbox providers respond over the first weeks.
If you have no intention of opening a DNS panel, this was the most hands-off option in the test.
Pricing sits in paid plans with that setup work bundled in, which is the whole value proposition.
What we liked
  • Authentication done for you, correctly, on day one.
  • Ramp speed that adapts instead of following a fixed schedule.
What we didn’t
  • You pay for setup help you only need once.

4. Mailwarm

Mailwarm does one job. It exchanges emails to build sender reputation, and the dashboard stays out of your way. You can set separate volume controls for Gmail and Outlook, which is more control than the simplicity suggests.
The tradeoff is reporting. You won’t get the spam placement breakdowns Mailreach and lemwarm give you, so when something goes wrong you’re guessing.
It’s a standalone per-inbox subscription.
What we liked
  • Separate volume controls per provider.
  • Nothing to learn.
What we didn’t
  • Reporting stops at “running”.

5. Warmup Inbox

Warmup Inbox lets several team members watch warmup progress across shared mailboxes, with an inbox health score per account. For a sales team babysitting six SDR inboxes, that shared view saves a weekly round of screenshots in Slack.
You can also customize warmup email content to match your industry, which several tools in this test don’t allow.
Pricing runs on standalone per-inbox plans with team access.
What we liked
  • Health scoring per mailbox in one shared dashboard.
  • Editable warmup content.
What we didn’t
  • The collaboration features are wasted if you’re warming one inbox.

6. Warmbox

Warmbox had the lowest starting price for an individual warming one or two inboxes. It ships with pre-built warmup recipes for a new domain, for reputation recovery, and for maintenance mode once you’re established.
Features thin out at the lower tiers, so read the plan before you commit.
Pricing is a standalone per-inbox subscription with a genuinely cheap entry point.
What we liked
  • Recipes that match the situation instead of one generic ramp.
  • The cheapest realistic starting point for a founder doing their own outreach.
What we didn’t
  • The entry tier leaves out most of the reporting.

7. Instantly Warmup

Instantly runs one of the largest peer networks I connected to. It includes AI read emulation that mimics human behavior on the receiving side, opening and scrolling before replying.
Warmup comes with the platform subscription, so there’s no extra cost and no separate login if Instantly already sends your campaigns.
What we liked
  • Network size, which showed in how quickly Gmail placement stabilized.
  • No separate warmup bill.
What we didn’t
  • Large networks mean less control over who your reputation is built with.

8. Smartlead Warmup

Smartlead allows unlimited mailbox warming across client accounts with no per-inbox fee, and the API lets you automate warmup setup whenever a new client domain comes online. For an agency, that removes the cost surprise that per-inbox pricing creates at scale.
The white-label option keeps the underlying tool invisible to clients, which matters more to some agencies than any deliverability metric.
Pricing is bundled into the platform subscription.
What we liked
  • Unlimited mailboxes under one flat platform cost.
  • API control for provisioning new domains.
What we didn’t
  • Overkill for a single team sending from a handful of inboxes.

9. Folderly

Folderly goes past warmup into deliverability consulting. The service audits your email setup end to end, covering DNS records, sending patterns, message content, and the specific words or formatting that trip spam filters. It then tells you what to change.
The price sits well above the pure warmup tools, and it’s closer to buying a service than buying software.
What we liked
  • Findings you can act on rather than a score.
  • Useful when the problem is upstream of warmup.
What we didn’t
  • Hard to justify if your only issue is a new domain.

10. TrulyInbox

TrulyInbox offered the lowest per-inbox price I found for basic warmup. The interface has no learning curve, because there’s very little to learn.
Reporting is limited next to the premium tools. If cost ranks above insight for you right now, it covers the fundamentals.
What we liked
  • The cheapest per-inbox rate in the test.
  • Fast setup.
What we didn’t
  • Minimal visibility into placement.

11. InboxAlly

InboxAlly takes a different route. Instead of a peer network, it uses real users who interact with your emails to train inbox providers, opening them, replying, and pulling messages out of spam into the inbox.
It worked best on accounts that had already been warmed but still saw spam placement, which makes it a reputation repair tool more than a warmup service.
Pricing is a standalone subscription, separate from whatever outreach platform you use.
What we liked
  • Genuinely different mechanism, useful when peer warmup has plateaued.
  • Strong at moving messages out of the spam folder.
What we didn’t
  • Not the tool you start a brand new domain with.

Also considered: four tools that didn’t make the tested 11

Four names come up often enough that leaving them unexplained would be dishonest.
Warmy.io pairs warmup with deliverability monitoring and inbox placement testing, so it competes most directly with Mailreach. Mailivery runs a peer-to-peer warmup network with sender reputation scoring. Mailstand focuses on connecting mailboxes into a shared warmup network, which appeals to teams warming many accounts at once. Snov.io bundles warmup into a wider sales platform alongside prospecting and sequences, so it belongs in the same category as lemlist, Instantly, and Smartlead.
I left them out of the tested 11 for one reason: three weeks per tool across three providers is a lot of inboxes, and I capped the test where I could still run every tool under identical conditions. If your shortlist includes any of them, the evaluation criteria below apply to them exactly as they do to the eleven above.

What email warmup is and why it matters for cold email

Email warmup is the process of raising sending volume gradually from a new or dormant email account while generating positive engagement along the way. The goal is a sender reputation solid enough with Gmail, Outlook, and Yahoo that your cold emails reach the primary inbox.
New domains start with no reputation at all. Inbox providers don’t trust an unknown sender, so they default to caution and watch what happens. They also track engagement closely, and an account with almost no opens and zero replies looks exactly like a spam operation. Warmup generates the activity those filters want to see, so by the time your first real campaign goes out, the algorithm already has a reason to trust you.

How email warmup tools actually work

Most warmup tools run on a peer network. Users exchange emails with each other, and when your warmup message arrives in another user’s inbox, their account opens it and sends a short reply.
If the message lands in spam, the receiving account pulls it out and marks it as not spam or as important. That signal tells the provider your mail is wanted, and repeated often enough across many accounts, it moves the needle on placement.
Volume then climbs over days and weeks to imitate a real sender growing into their sending habit. Better tools add provider matching, sending Gmail to Gmail and Outlook to Outlook, because reputation signals stay cleaner when the route matches the one your campaigns will use.
None of it replaces authentication. The M3AAWG anti-abuse working group treats SPF, DKIM, and DMARC as the baseline any bulk sending program is expected to meet before anything else, and warmup sits on top of that baseline rather than substituting for it.

How to choose the right email warmup tool

Network size and inbox quality

Larger peer networks produce more varied engagement signals, and a tool exchanging mail with thousands of real inboxes trains providers faster than one working from a small pool.
Quality counts as much as size. Real business inboxes read as legitimate in a way throwaway accounts never will. When you’re evaluating a vendor, ask directly whether the network is made of actual users of the product.

Spam placement and deliverability reporting

Knowing where your mail lands is what makes troubleshooting possible. Some tools show you “warmup running” and nothing else. Others break placement down by provider and by day.
If you’re diagnosing a problem, you need the detail. If warmup is a background process you’ll check monthly, basic reporting will do. lemlist puts that reporting next to campaign data through Monitoring & alerts, so a placement drop shows up as a notification instead of a discovery you make three weeks later.

Provider matching and human sending patterns

Sending Gmail to Gmail and Outlook to Outlook creates cleaner reputation signals than routing everything through one pool. Sending behavior matters just as much, and the tools that performed best spread sends across the day, waited a realistic interval before replying, varied subject lines and body copy, and kept per-inbox volume uneven rather than identical.
Tools that mimic real behavior beat tools that fire at predictable intervals with the same message every time.

Monitoring after warmup ends

This is the criterion most roundups skip, and it’s the one that costs people money. Warmup gets you to a good starting reputation. Campaigns then put that reputation under load, and reputation decays quietly when something breaks upstream, like a DNS change, a bad list, or a spike in complaints.
I’d rather have a mediocre warmup network with continuous monitoring than a great network that goes silent the day campaigns start. Inside lemlist, warmup, deliverability setup, and monitoring run as one workflow, so the same system that built the reputation keeps testing placement afterwards and tells you when it slips. Standalone warmup tools can monitor too, but you’ll be stitching two products together and reconciling their numbers yourself.

Pricing per mailbox

Two models exist. Per-inbox fees suit small teams with a handful of senders. Flat rates with unlimited mailboxes favor agencies and teams with many senders, where per-inbox pricing turns into a budget problem fast.
lemlist, Instantly, and Smartlead all include warmup in the platform subscription, which removes the question entirely.

Integration with your cold email platform

Native warmup, built into the tool that sends your campaigns, avoids sync issues and lets the system coordinate volume between warmup and outreach automatically. Standalone tools need managing on their own.
If lemlist, Instantly, or Smartlead already sends your sequences, use their warmup. If your outreach runs somewhere else, a standalone service like Mailreach or Warmbox does the job fine.

Common email warmup mistakes that hurt deliverability

  • Starting campaigns before warmup has finished pushes an inbox to full volume too early, and spam filters read that jump exactly as you’d expect.
  • Running warmup and outreach at full speed from the same inbox on the same day confuses the reputation signals you spent weeks building.
  • Filling warmup emails with generic or sales-heavy copy can drag your reputation down instead of lifting it, because the content still gets scored.
  • Skipping authentication wastes the entire exercise, since warmup won’t save you if SPF, DKIM, and DMARC aren’t configured correctly on the sending domain.
  • Warming a domain that’s already blacklisted rarely works, so fix the underlying cause first and run your records through lemlist’s deliverability setup checker before you spend three weeks warming something that’s beyond saving.

Frequently asked questions about email warmup tools

Does email warmup actually work to improve inbox placement?

Yes. Warmup builds sender reputation by generating the engagement signals inbox providers use to decide placement, and the effect is measurable in inbox versus spam rates before and after. In our three-week test, every tool improved primary-tab placement on Gmail.

How long should you warm up a new email account before sending cold emails?

Two to four weeks is the standard recommendation, and it matched what I saw. Your exact timeline depends on the volume you’re ramping toward and how the providers respond to your early sends.

Can email warmup recover a domain that’s already been flagged as spam?

Usually not on its own. You have to fix whatever caused the flag in the first place, whether that’s a list full of unverified addresses, a complaint rate climbing because your targeting is off, or authentication records that were never set up properly. In many cases the practical move is sending from a fresh domain while the damaged one ages out of the filters’ memory.

Is email warmup compliant with Google and Yahoo sender requirements?

Warmup tools operate within provider terms of service as long as they use real inboxes and genuine engagement. The bigger compliance question is whether your actual campaigns meet the authentication and unsubscribe rules in Google’s bulk sender guidelines and Yahoo’s sender requirements, because that’s where accounts get throttled.

Can I warm up my email for free?

Sort of. Free standalone warmup tools are rare and heavily limited, usually capped at a few sends a day on one mailbox. The realistic free route is a platform trial where warmup is included, which is how lemwarm works during lemlist’s 14-day trial. You can also warm manually by emailing colleagues and contacts who reply, though at any real volume the time cost outweighs the subscription.

How many emails a day should I send during and after warmup?

Warmup tools typically start at a handful of sends per inbox per day and add a few more each day, which is why the ramp takes weeks. Once you’re live, keep per-inbox volume modest and add mailboxes instead of pushing one account harder. A sudden jump from warmup volume to full campaign volume is the single most common way people undo their own work.

Do I need a separate warmup tool if my sending platform already includes one?

In most cases, no. Native warmup coordinates with your campaign volume automatically, which a standalone tool can’t do. The exception is diagnosis: if you’re chasing a placement problem and your platform’s reporting stops at a progress bar, a tool like Mailreach earns its cost by telling you which provider is filtering you.

Should warmup keep running after campaigns start?

Yes, at a reduced level. Reputation is maintained, not won once. Most teams leave warmup running permanently at lower volume so engagement continues on days when campaigns are paused.

Can I warm up several inboxes at the same time?

You can, and agencies do it constantly. Watch the pricing model when you do, because per-inbox fees that look reasonable for two mailboxes become the largest line in your outbound budget at thirty. Flat-rate platforms handle that case better.

Does warmup work the same on Outlook as on Gmail?

Not quite. Across the test, Outlook and custom SMTP domains warmed more slowly than Gmail on the same schedule. If Microsoft 365 is your main sending environment, give the ramp more time and pick a tool that does provider matching rather than pooling all sends together.

Over to you

Warmup is table stakes for cold outbound, and the good news is that the choice is less dramatic than eleven reviews make it look. Pick based on where your campaigns already run, then on how much visibility you need when something goes wrong.
If you want warmup, placement monitoring, and campaign sending to live in one workflow instead of three tabs, Start a 14-day free trial of lemlist (no credit card required) and see how lemwarm behaves on your own domain.
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