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.

The process works by connecting your email account to a network of thousands of other users running the same warmup software. Your account sends emails to these addresses, they open your messages, mark them as important, reply to them, and pull them out of spam folders if they land there. This creates positive engagement signals that teach email service providers your domain is legitimate.

Think of it like building credit history. A new domain has no reputation-it's neutral. Email providers don't know if you're a legitimate business or a spammer. Warmup builds that history through consistent, positive interactions over weeks.

How Email Service Providers Judge Your Reputation

Before diving into specific tools, you need to understand what actually affects your sender reputation. Email providers like Gmail, Outlook, and Yahoo use complex algorithms to determine whether your emails deserve the inbox or spam folder.

They track your engagement rates-how many people open your emails, reply to them, mark them as important, or move them to folders. High engagement signals legitimacy. They also monitor complaint rates-how many recipients mark your emails as spam or unsubscribe immediately. Even a 0.1% spam complaint rate can damage your reputation.

Sending patterns matter enormously. If you send 5 emails on Monday, 200 on Tuesday, and 10 on Wednesday, that erratic behavior looks suspicious. Warmup tools solve this by ramping up volume gradually and maintaining consistent daily sending.

Your technical setup plays a role too. Email providers check your SPF, DKIM, and DMARC records to verify you're authorized to send from your domain. If these authentication protocols aren't properly configured, even warmed accounts will struggle with deliverability.

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 system handles mailbox rotation automatically, distributing your sends across multiple accounts to protect individual domain reputations. The unified inbox consolidates all replies in one place regardless of which sending account received them.

Smartlead's warmup runs continuously in the background. You can set custom warmup limits per account, and the system gradually increases sending volume based on your domain age and current reputation. The warmup emails use natural language generated through AI to avoid detection patterns.

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. The platform also assumes you're doing cold outreach at scale. If you're sending under 50 emails per day, you're probably overpaying for features you don't need.

Try Smartlead

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 system includes a slow ramp feature that gradually increases volume starting from just 2 emails on day one, then 4 on day two, building up slowly to protect your domain. The platform uses headless browsers to simulate human reading behavior-spending time on emails and scrolling through them rather than instantly opening and closing.

You can customize your warmup settings extensively. Set specific open rates, reply rates, and spam protection levels. The system lets you randomize daily sending volume so you're not sending exactly the same number every day, which looks more natural to email providers.

One feature that stands out is ESP matching. Instantly can automatically match your sending domain with warmup partners using the same email provider. If you're sending from Gmail, you get more warmup interactions with other Gmail accounts, which builds provider-specific reputation faster.

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.

Try Instantly

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.

Lemwarm was actually the original email warmup service that popularized this approach. When it launched, the concept of automated warmup networks was new. Other tools on this list emerged as competitors to Lemwarm's early success.

The network consists of premium inboxes with established reputations. Lemwarm generates conversation threads that look natural, avoiding the obvious patterns that spam filters can detect. The emails include contextually relevant subject lines and body content rather than obvious placeholder text.

One interesting aspect of Lemwarm is its Smart Cluster feature, which groups your warmup activity with other users in similar industries and sending patterns. The idea is that warming up with contextually relevant senders improves reputation faster than random interactions. In practice, this feature doesn't always deliver significant advantages over standard warmup networks.

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.

Try Lemlist

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.

Mailreach stands out for its attention to realistic behavior patterns. The warmup emails include contextually relevant content and follow natural timing patterns. They vary subject lines extensively to avoid detection. The system avoids obvious warmup signals like identical subject line codes or unnatural sending patterns that could trigger spam filters.

The network includes over 20,000 high-reputation inboxes across Google Workspace and Office 365 accounts. These aren't throwaway Gmail addresses-they're established accounts with existing positive reputations, which helps your warmup activity look more legitimate.

Mailreach provides inbox placement testing as a separate feature. You can send test emails to their seed list of real addresses and get detailed reports on where your messages land across different email providers. This helps you verify your warmup is actually working before you start real campaigns.

The dashboard shows your reputation score for each major ESP along with trend analysis over time. You can track improvement week by week and identify if specific providers are treating your emails differently.

One limitation: the interface can slow down when managing 30+ inboxes simultaneously. Users also mention the lack of bulk editing features makes account management tedious at scale. For agencies handling multiple client domains, this becomes frustrating.

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.

The network includes 35,000+ inboxes to send warmup emails to. Warmbox uses GPT-4 technology to generate warmup email content, so every email looks different and uses natural language. This matters because email providers can detect patterns-if every warmup email looks identical or uses the same phrases, spam filters notice.

You get four warmup recipes to choose from: Grow Progressive (default), Grow Fast, Maintain, and Custom. Most users stick with Grow Progressive, which gradually increases volume over several weeks. The Grow Fast option ramps up more aggressively but carries higher risk if your domain has any existing issues.

Warmbox provides detailed analytics on your warmup progress. You can track your reputation score, see how many emails are being sent daily, monitor spam folder placement, and review engagement metrics. The dashboard shows trends over time so you can verify your reputation is improving.

One feature worth noting is timezone and working hours customization. You can set your warmup emails to only go out during normal business hours in your timezone, which makes the activity look more realistic to email providers.

The main criticism is the lack of user reviews on major platforms like G2, Capterra, and Trustpilot. There's limited social proof compared to competitors, which makes it harder to verify long-term reliability. Some users on Product Hunt reported emails still landing in spam even after using Warmbox, though these reviews are dated.

Warmup Inbox

Warmup Inbox is a dedicated warmup service with a network of 30,000+ active email accounts. It's known for straightforward pricing and simple setup.

Pricing is $19/month per inbox (or $15 when billed annually). The Basic plan includes essential warmup features. The Pro plan at $49/month per inbox adds advanced options like ESP-specific warmup, scheduled warmup, and language-specific warmup in five different languages.

The platform uses AI to generate personalized warmup emails, which are then audited by staff to ensure quality. The system automatically sends emails, generates replies, marks messages as important, and pulls emails out of spam folders.

Warmup Inbox provides reputation score tracking with community benchmarks. You can see how your sender reputation compares against other users and get alerts when your score drops below set thresholds. This early warning system lets you pause campaigns before causing serious damage.

One interesting feature is topic-specific warmup, which tailors warmup email content to match your industry or outreach focus. The idea is that warming up with contextually relevant content better prepares your domain for actual campaigns. Language-specific warmup lets you send warmup emails in different languages if you're targeting international markets.

The setup process is genuinely simple-most users report being live in under 10 minutes. You connect your account, choose settings, and it runs automatically. The reporting dashboard provides clear data on warmup progress without overwhelming you with unnecessary metrics.

User reviews consistently mention the responsive support team. When issues arise, you typically get help within minutes rather than hours or days. For a warmup service where timing matters, this responsiveness is valuable.

The main drawback is per-inbox pricing adds up quickly for teams managing multiple accounts. If you need to warm up 10 inboxes, you're paying $150-190/month. Competitors offering unlimited warmup for a flat fee become more economical at that scale.

Some users also report that warmup emails look computer-generated and potentially spammy, which raises concerns about whether the warmup activity itself could hurt reputation. A few negative reviews mention email accounts getting blocked shortly after starting warmup, though these represent a small percentage of overall feedback.

TrulyInbox

TrulyInbox is an email warmup tool that stands out for one major reason: unlimited email accounts on all plans. While most competitors charge per inbox, TrulyInbox lets you connect as many accounts as you need for a flat monthly price.

Pricing starts at $29/month for the basic paid plan. You can connect unlimited email accounts for warmup even on this entry tier. TrulyInbox also offers a forever-free plan that lets you test the service before committing to paid features.

The platform mimics human-like sending behavior with a network of high-reputation inboxes. It sends emails one at a time at varying intervals to boost sender reputation gradually. As your reputation improves, the system increases email frequency for better inbox placement.

TrulyInbox provides a deliverability score that lets you track inbox reputation and deliverability rate. This allows you to monitor your sending pattern and verify that warmup is working as expected.

The service supports all major email providers including Gmail, Google Workspace, Office 365, Outlook, Yahoo, Zoho, and others. Setup is straightforward through OAuth for Google and Microsoft accounts, with SMTP/IMAP configuration available for other providers.

One advantage for agencies and teams is the ability to integrate TrulyInbox with cold email software and manage all accounts from a single platform. This consolidation simplifies workflows when you're managing warmup for multiple clients or domains.

The customization options are comprehensive. You can control how many emails to send, set reply rates, adjust daily ramp-up volume, and customize other parameters to match your specific needs. This flexibility helps you tailor warmup to your situation rather than accepting one-size-fits-all defaults.

User reviews highlight the platform's cost-effectiveness for teams managing multiple inboxes. Where paying $25 per inbox quickly becomes expensive, TrulyInbox's unlimited model keeps costs predictable regardless of scale. The interface is clean and user-friendly without unnecessary complexity.

The main limitation is the 7-day free trial on paid plans, which is shorter than some competitors. However, the forever-free plan partially addresses this by letting you test core functionality indefinitely, even if with limited features.

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 need to warm up many accounts cost-effectively: TrulyInbox makes the most sense with unlimited accounts for a flat fee. The per-inbox pricing of other standalone tools gets expensive fast when you're managing 10+ domains.

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 Lemlist all have adequate warmup included. Focus on your sending strategy, not warmup optimization.

For agencies managing client accounts: TrulyInbox or Instantly offer the best economics. Both support unlimited accounts, but Instantly includes full sending infrastructure while TrulyInbox focuses purely on warmup and costs less.

Understanding Warmup Networks

All warmup tools rely on networks of real email accounts exchanging messages. The size and quality of these networks directly impacts warmup effectiveness.

Network size matters, but quality matters more. A network of 50,000 established, high-reputation inboxes beats 100,000 throwaway Gmail accounts created specifically for warmup. Email providers can detect patterns when warmup activity comes primarily from new, low-activity accounts.

The best warmup networks include diverse email providers. Your warmup should include interactions with Gmail, Outlook, Yahoo, and custom domain addresses. If you only warm up against Gmail accounts but then send campaigns primarily to Outlook recipients, you're building reputation with the wrong provider.

Geographic diversity helps too. Warmup networks that span multiple countries and languages create more natural-looking activity patterns. This becomes especially important if you're targeting international markets.

Some tools use peer-to-peer networks where everyone using the service contributes their inbox to the pool. Others maintain dedicated warmup accounts. Peer-to-peer networks tend to have higher-quality accounts since they're real business addresses, but they also mean your warmup partners are other cold emailers who might have their own reputation issues.

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. New domains have zero reputation, so providers treat them with maximum suspicion. Rushing this process almost guarantees spam folder placement.

Established domain with good history: 1-2 weeks to prepare for increased sending volume. If your domain has been sending normal business email for months and you want to start cold outreach, warmup builds on existing positive reputation. You're not starting from zero, so improvement comes faster.

Domain with spam issues: 6-8 weeks to rebuild reputation, assuming you've fixed whatever caused the spam flags in the first place. If your domain got flagged because of purchased lists, spammy content, or authentication issues, warmup alone won't fix it. You need to address the root cause first, then spend extended time rebuilding trust.

Dormant domain: 3-4 weeks to reactivate. If you have a domain that was previously active but hasn't sent email in months, providers have essentially forgotten about you. You need to re-establish reputation, but it's faster than starting fresh.

Don't rush this. Warmup isn't a checkbox-it's ongoing maintenance. Keep it running even after you start sending campaigns. Many people make the mistake of running warmup for a few weeks, starting their campaigns, then stopping warmup entirely. This causes reputation to decay over time.

Warmup Volume and Campaign Volume

Your warmup volume and actual campaign sending volume need to align. This is one of the most common mistakes people make with email warmup.

If your warmup is set to 30 emails per day and you suddenly start sending 200 cold emails daily, you'll tank your deliverability immediately. Email providers notice the sudden spike and flag you as suspicious. Your actual sending volume should stay within or slightly below your warmup targets.

Build a buffer. If you plan to send 100 cold emails per day, warm up to 120-150 daily. This gives you headroom for occasional higher-volume days without triggering red flags.

Account for total volume across all your sending. If you're warming up one account but rotating sends across five accounts, each individual account only needs warmup for its share of the volume. However, domain reputation matters too, so some warmup activity should occur on all accounts even if they're not all sending campaigns simultaneously.

When scaling up, increase gradually. Don't jump from 50 to 200 emails per day overnight. Increase by 10-20% per week while monitoring your deliverability metrics. If you see declining open rates or increasing bounces, you're scaling too fast.

Common Warmup Mistakes

Stopping warmup once you start sending real campaigns: Bad idea. Keep warmup running continuously to maintain your sender reputation. The warmup creates positive engagement signals that offset the inevitable spam complaints and non-engagement from cold campaigns. Stop warmup and your reputation starts sliding backward.

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. This is one of the fastest ways to destroy reputation you spent weeks building.

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. No amount of warmup can overcome terrible list quality or content that triggers spam filters.

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. The reputation you build is specific to your sending path.

Using identical warmup settings across all accounts: Different domains and email accounts have different histories and reputations. A brand new domain needs slower, more conservative warmup than an established domain. Customize your settings based on each account's specific situation rather than applying blanket settings.

Ignoring engagement metrics during warmup: Most tools provide reputation scores and deliverability metrics. If your scores aren't improving after 2-3 weeks, something's wrong. Check your technical setup, review your warmup settings, or contact support. Don't just assume it's working if the data says otherwise.

Sending campaigns from accounts that aren't fully warmed: Impatience kills cold email campaigns. Waiting an extra week or two for proper warmup is always better than launching early and burning your domain. Once you damage reputation severely, recovery takes months.

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. The natural email activity from your regular business communications provides sufficient engagement signals.

If you're sending 50+ cold emails per day: Yes. At this volume, deliverability becomes your bottleneck. Warmup is non-negotiable. Without it, you'll see declining open rates within days as more emails hit spam folders.

If you're using new domains or email accounts: Absolutely. Fresh domains have zero reputation. Without warmup, you're starting in the spam folder. Even if your content is perfect and your list is clean, providers don't trust new senders.

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 positive engagement from actual customers will build reputation organically.

If you've had deliverability issues in the past: Yes, but fix the underlying problems first. Warmup can rebuild reputation, but only if you've addressed what caused the issues initially. If you just start warmup without fixing bad practices, you'll damage reputation again immediately.

If you're doing LinkedIn or other social outreach and occasionally sending follow-up emails: Probably not necessary. The low volume of genuine business correspondence doesn't require dedicated warmup infrastructure. Just send normally and maintain good practices.

Technical Setup That Matters

Warmup tools can't fix broken technical setup. Before investing in warmup services, verify your domain authentication is properly configured.

SPF (Sender Policy Framework) tells email providers which servers are authorized to send email from your domain. Without a proper SPF record, providers can't verify you're legitimate. Check your SPF record covers all your sending sources-your email platform, warmup tool, and any other services sending from your domain.

DKIM (DomainKeys Identified Mail) adds a digital signature to your emails that proves they haven't been tampered with. This cryptographic verification helps providers trust your messages. Most email platforms handle DKIM automatically, but verify it's working before starting warmup.

DMARC (Domain-based Message Authentication, Reporting, and Conformance) tells providers what to do with emails that fail SPF or DKIM checks. Start with a monitoring-only policy to collect data, then move to quarantine or reject policies once you've verified everything is working correctly.

Custom domains beat generic email providers for cold outreach. Sending cold emails from @gmail.com looks less professional and gives you less control over reputation. Purchase a domain specifically for cold outreach so issues don't affect your main business domain.

Separate sending domains from your main business domain. If your company website is acme.com, send cold emails from acmesales.com or similar. This isolation protects your primary domain reputation if cold outreach encounters problems.

Monitoring Deliverability

Warmup tools provide reputation scores, but you should also monitor actual campaign performance to verify deliverability.

Track open rates consistently. If open rates suddenly drop 30-40%, you likely have a deliverability problem. Your emails are hitting spam folders instead of inboxes. This happens before you'll see changes in bounce rates, so it's an early warning signal.

Monitor spam complaint rates. Most email platforms report how many recipients marked your emails as spam. Keep this under 0.1%. Even 0.3-0.5% is enough to damage reputation significantly. If complaints spike, pause campaigns immediately and investigate.

Watch bounce rates carefully. Hard bounces (invalid addresses) and soft bounces (full inboxes, temporary issues) both affect reputation. Keep total bounce rate under 3-5%. Higher bounce rates signal you're sending to low-quality lists.

Use seed testing to verify inbox placement. Send test emails to your own accounts across different providers before launching campaigns. If your tests hit spam folders, your real campaign emails will too.

Google Postmaster Tools provides detailed data on your sending reputation with Gmail. You can see your domain reputation, IP reputation, spam rate, and feedback loop data. This free tool gives insight into how Gmail specifically views your sending.

Microsoft SNDS (Smart Network Data Services) offers similar data for Outlook and Hotmail. Register your sending IPs to get reputation data and spam trap hits. This helps you identify problems before they become severe.

Cost Analysis

The real cost of warmup includes not just subscription fees but also opportunity cost and potential domain replacement.

Bundled warmup with cold email platforms (Smartlead, Instantly, Lemlist) looks expensive at $40-100/month, but you're paying for full sending infrastructure. If you need both warmup and sending, bundled platforms provide better value than buying services separately.

Standalone warmup with per-inbox pricing (Mailreach at $25/account, Warmup Inbox at $15-19/account) works well for 1-5 accounts. Beyond that, costs escalate quickly. Ten accounts cost $150-250/month for warmup alone.

Flat-fee unlimited warmup (TrulyInbox at $29/month) provides the best economics for agencies and teams managing many accounts. The cost stays fixed regardless of how many domains you're warming up.

The hidden cost is time. If warmup fails and you burn a domain, you need to purchase a new domain, set up all technical records, wait for it to age slightly, then start warmup from scratch. This easily represents $50-100 in hard costs plus weeks of lost time. Reliable warmup saves this expense.

Compare warmup costs to your revenue per campaign. If each successful cold email campaign generates $5,000-10,000 in closed business, spending $50-100/month on warmup is trivial insurance. If you're sending low-value campaigns, minimize warmup costs accordingly.

Scaling Multiple Accounts

Serious cold emailers use multiple email accounts to spread volume and protect individual domain reputations. Warmup strategy changes when managing many accounts.

Start with 3-5 accounts minimum. This lets you rotate sending to keep individual account volume reasonable. If you need to send 150 emails daily, three accounts sending 50 each works better than one account blasting 150.

Warm all accounts simultaneously, even if you're not using them all yet. When an account sits idle after warmup, reputation decays. It's easier to maintain warmup continuously than stop and restart.

Stagger warmup start dates slightly. Don't connect ten brand new domains to warmup on the same day-it looks suspicious if all your domains suddenly spring to life simultaneously. Space new account creation by a few days or weeks.

Use consistent naming conventions. If your accounts are [email protected], [email protected], [email protected] with similar content, providers may link them together. Some reputation damage could spread across accounts. Vary the names, domains, and content enough to maintain separation.

Monitor aggregate reputation across all accounts. If 3 of your 5 accounts see declining deliverability simultaneously, you likely have a systemic issue with your list quality, content, or sending practices rather than individual account problems.

When to Pause or Stop Warmup

Most warmup should run continuously, but some situations require pausing or stopping.

Pause warmup if your reputation score drops significantly. Most tools show reputation on a 0-10 scale. If you drop below 7-8, stop real campaigns and let warmup work without the additional strain of actual sends. Resume campaigns once reputation recovers.

Stop warmup if email providers suspend or limit your account. If Gmail disables your account for suspicious activity, warmup likely contributed to the problem. Disconnect immediately, contact provider support, and resolve the underlying issue before considering warmup again.

Pause during extended non-sending periods. If you're not running campaigns for a month, reduce warmup volume significantly but don't stop entirely. Keeping some activity prevents reputation decay without wasting resources.

Stop warmup on accounts you're retiring. If you're phasing out a domain or email account, no need to continue paying for warmup. Let it wind down naturally.

Never stop warmup on active sending accounts just to save money. The cost of warmup is trivial compared to the revenue loss from declining deliverability. This is the worst place to cut costs.

Alternative: Manual Warmup

You can warm up email accounts manually without paid tools, but it's tedious and time-consuming.

Start by sending 3-5 emails daily to real people who will open and reply. Increase by 2-3 emails daily every few days. Reach your target volume after 4-6 weeks. Every email should get opened and ideally replied to, so reach out to colleagues, friends, or business contacts who will engage.

Vary your content significantly. Don't send the same message repeatedly-providers detect patterns. Write unique emails with different subject lines, content length, and formatting.

Include normal business correspondence in your warmup. If you're sending invoices, project updates, or customer communications from the account, that counts as positive engagement.

Pull emails out of spam folders manually. Have your warmup partners check their spam folders and move your messages to inbox if they landed there. This trains the algorithms that your emails belong in the inbox.

The problem with manual warmup is sustainability. You need to do this every single day for weeks, then maintain ongoing activity even while running campaigns. Most people can't maintain the discipline, which is why automated tools exist.

Manual warmup makes sense if you're only warming one account, you're on an extremely tight budget, and you have the time and discipline to execute consistently. For everyone else, paying $15-30/month for automated warmup is worth it.

Red Flags That Warmup Isn't Working

Sometimes warmup fails despite following best practices. Watch for these warning signs.

Open rates declining over time despite ongoing warmup indicates your emails are increasingly hitting spam folders. The warmup isn't building reputation fast enough to offset natural decay or campaign-related reputation damage.

Reputation scores stagnant after 3-4 weeks suggests something's wrong with your technical setup or the warmup tool itself. You should see gradual improvement week by week. Flat scores mean the warmup activity isn't generating the expected positive signals.

Sudden account suspensions or limits from email providers during warmup period usually means the warmup traffic looks suspicious. Either the tool is using low-quality warmup accounts or the volume ramped too aggressively.

Warmup emails landing in your spam folder is an ironic but serious problem. If the warmup traffic itself gets flagged as spam, it's actively hurting rather than helping reputation. Disconnect immediately and choose a different tool.

If you see any of these signs, don't just continue hoping things improve. Stop, investigate the root cause, fix it, then restart warmup from scratch if necessary.

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 (1-5 accounts), Warmbox for mid-size operations (5-15 accounts), or TrulyInbox if you're managing many accounts and want flat-rate pricing.

For agencies managing multiple clients: TrulyInbox's unlimited model or Instantly's bundled platform offer the best economics at scale.

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.