Best Email Warmup Tools
If you're sending cold emails at any kind of volume, you need email warmup. Without it, your emails land in spam and your domain reputation tanks. The question isn't whether you need warmup—it's which tool to use.
I've tested the major players. Here's what actually works, what costs what, and which one you should pick based on your situation.
What Email Warmup Actually Does
Email warmup tools gradually increase your sending volume while maintaining positive engagement signals. They send emails from your account to a network of real inboxes, those inboxes open and reply to your emails, and your domain builds a reputation with email providers as a legitimate sender.
Without warmup, if you suddenly start sending 200 cold emails a day from a fresh domain, Gmail and Outlook will flag you as spam immediately. Warmup solves this by making your domain look like it's been sending and receiving legitimate email for months.
Smartlead
Smartlead combines email warmup with cold email sending in one platform. The warmup feature is included with all plans and works across unlimited email accounts.
The warmup network has over 200,000 inboxes. Your emails get sent to real accounts, opened, moved out of spam folders, and replied to. The system automatically adjusts based on your domain's reputation score.
Pricing starts at $39/month for the Basic plan (2,000 leads), $79/month for Popular (30,000 leads), and $94/month for Pro (100,000 leads). The warmup feature is included—you're not paying extra just for warmup if you're already doing cold email.
The big advantage here is integration. If you're running cold email campaigns, you can manage both warmup and sending in one place. The downside is you're locked into Smartlead's sending infrastructure—if you want to use a different cold email tool, you'll need separate warmup.
Instantly
Instantly offers warmup as part of their cold email platform. Like Smartlead, it's bundled with the sending features.
The warmup network includes thousands of real email accounts. You can warm up unlimited email accounts on any plan. The system handles opens, replies, and positive engagement signals automatically.
Pricing is $37/month for the Growth plan (1,000 leads), $97/month for Hypergrowth (25,000 leads), and custom pricing for enterprise. Again, warmup is included—not an add-on.
Instantly's warmup is solid but not as aggressive as some standalone options. If you're already using Instantly for cold email, keep using their warmup. If you're shopping around, the main decision is whether you want Instantly's sending features or prefer a different setup.
Lemlist
Lemlist includes email warmup (called Lemwarm) with all paid plans. It's another all-in-one cold email platform with integrated warmup.
Lemwarm connects to a network of real users who also use the feature. Your emails get sent, opened, and replied to. The system claims to improve deliverability within 2-4 weeks.
Pricing starts at $59/month for Email Starter, $99/month for Email Pro, and $159/month for Multichannel Expert. Warmup is included on all plans.
The limitation here is you need to be a Lemlist customer to use Lemwarm. If you're committed to Lemlist's cold email approach, the bundled warmup makes sense. If you're using other tools, you'll need a different warmup solution.
Mailreach (Standalone Warmup)
Mailreach is pure warmup—no cold email sending, no extra features. You connect your email accounts and it handles warmup across multiple providers.
The tool works with Gmail, Outlook, SMTP, and most major email providers. It gradually increases your sending volume, manages reply conversations, and provides deliverability scoring.
Pricing is $25/month per email account. That's it. Simple, transparent, pay per inbox.
This is the best option if you're already committed to a specific cold email tool and just need warmup. The per-account pricing gets expensive if you're warming up 10+ inboxes, but for small teams running 2-5 email accounts, it's the cleanest solution.
Warmbox (Standalone Warmup)
Warmbox is another standalone warmup service. It focuses exclusively on improving deliverability without the bloat of additional features.
The system sends emails from your account to their network, manages replies, and adjusts sending patterns based on your domain's performance. It works with Gmail, Outlook, and custom SMTP.
Pricing starts at $15/month for one email account, $49/month for up to 5 accounts, and $99/month for up to 15 accounts. Volume discounts make it cheaper per account as you scale.
Warmbox is cheaper than Mailreach if you're warming up multiple accounts. The interface is straightforward—connect your emails, set your targets, and let it run. If you need standalone warmup for a larger team, this pricing model makes more sense than paying $25/account elsewhere.
Which One to Pick
If you're using Smartlead, Instantly, or Lemlist for cold email: Use their built-in warmup. You're already paying for it, and having warmup integrated with your sending tool means fewer moving parts.
If you're using a different cold email tool or building your own system: Go with Mailreach (1-4 accounts) or Warmbox (5+ accounts). Standalone warmup gives you flexibility to switch sending tools without rebuilding your warmup infrastructure.
If you're just getting started with cold email: Pick your cold email platform first, then use whatever warmup comes with it. Don't overthink this—Smartlead, Instantly, and Reply all have adequate warmup included. Focus on your sending strategy, not warmup optimization.
How Long Warmup Takes
Most tools claim 2-4 weeks for noticeable deliverability improvements. In reality, it depends on your domain age, previous sending history, and target volume.
Brand new domain: 4-6 weeks minimum before sending serious volume. Start slow, let the warmup run continuously.
Established domain with good history: 1-2 weeks to prepare for increased sending volume.
Domain with spam issues: 6-8 weeks to rebuild reputation, assuming you've fixed whatever caused the spam flags in the first place.
Don't rush this. Warmup isn't a checkbox—it's ongoing maintenance. Keep it running even after you start sending campaigns.
Common Warmup Mistakes
Stopping warmup once you start sending real campaigns: Bad idea. Keep warmup running continuously to maintain your sender reputation.
Sending way more than your warmup volume: If your warmup is at 30 emails per day and you send 200 cold emails, you'll tank your deliverability. Your actual sending volume should stay within or slightly below your warmup targets.
Using warmup as a band-aid for bad sending practices: Warmup won't save you if you're sending to purchased lists, using spammy copy, or ignoring unsubscribe requests. Fix your fundamentals first.
Warming up with one provider but sending with another: If you warm up a Gmail account but send cold emails through an SMTP relay, you're not building reputation where it matters. Warm up using the same infrastructure you'll use for actual campaigns.
Do You Really Need Warmup?
If you're sending under 20 emails per day from an established domain with good history: Probably not. Your domain can handle low-volume sending without dedicated warmup.
If you're sending 50+ cold emails per day: Yes. At this volume, deliverability becomes your bottleneck. Warmup is non-negotiable.
If you're using new domains or email accounts: Absolutely. Fresh domains have zero reputation. Without warmup, you're starting in the spam folder.
If you're sending transactional or marketing emails to opted-in lists: Warmup helps but isn't critical. You're already getting natural engagement from real users. Focus on list quality and permission-based sending.
The Bottom Line
Email warmup isn't sexy, but it's mandatory for cold email at scale. The specific tool matters less than having warmup running consistently and matching your warmup volume to your actual sending.
For most people: Use whatever warmup comes with your cold email platform. Smartlead, Instantly, and Lemlist all include it.
For people who need standalone warmup: Mailreach for small teams, Warmbox for larger operations.
Stop overthinking warmup tools and focus on the stuff that actually moves the needle—your list quality, your copy, and your offer. Warmup just makes sure your emails land in the inbox. What happens after that is on you.
Looking for more cold email resources? Check out our guides on best cold email software and best cold email tools.