Best Email Warmup Tools in 2026: Tested and Compared
Email warmup is the single most important step before sending cold emails. Without it, your carefully crafted outreach goes straight to spam. We tested every major warmup tool to help you choose the right one.
What Is Email Warmup?
Email warmup gradually increases your sending volume on a new mailbox by exchanging emails with a network of real inboxes. These emails get opened, replied to, and moved out of spam — signaling to Gmail and Outlook that your account is trustworthy.
Skipping warmup is the number-one reason new cold email campaigns fail.
The Best Warmup Tools Compared
1. Instantly (Built-In Warmup)
Instantly's warmup is included with every paid plan starting at $30/month. It uses a network of 500,000+ real accounts.
Pros: No extra cost, seamless integration with sending, automatic warmup management, large network. Cons: Only available to Instantly users, less configuration than standalone tools. Best for: Teams using Instantly as their sending platform.
2. Warmbox
Warmbox is a dedicated warmup tool with advanced reputation scoring and multiple warmup recipes.
Pros: Deep analytics, custom warmup schedules, works with any sending platform, DNS health checks. Cons: Additional cost ($15-49/mo), separate tool to manage. Best for: Agencies and advanced senders who need granular control.
3. MailReach
MailReach combines warmup with deliverability monitoring in one tool.
Pros: Warmup + inbox placement testing, email health score, works with any provider, good reporting. Cons: Higher price point, some features only on higher plans. Best for: Teams that want warmup and monitoring in one place.
4. Lemwarm
Lemwarm is Lemlist's built-in warmup feature, included with paid plans.
Pros: Integrated with Lemlist sequences, no setup needed, automatic. Cons: Only for Lemlist users, less transparent about network size. Best for: Lemlist users.
| Tool | Price | Network Size | Standalone? | Monitoring |
|---|---|---|---|---|
| Instantly | Included ($30/mo+) | 500K+ accounts | No | Basic |
| Warmbox | $15-49/mo | 35K+ accounts | Yes | Advanced |
| MailReach | $25-99/mo | 20K+ accounts | Yes | Advanced |
| Lemwarm | Included ($59/mo+) | Unknown | No | Basic |
How Long Does Warmup Take?
For a brand-new mailbox: - Days 1-7: Start at 5-10 emails/day, gradual increase - Days 7-14: Ramp to 30-40 emails/day - Day 14+: Ready for campaigns (keep warmup running alongside)
For a dormant mailbox (not used for 30+ days): 7-10 days of warmup is typically sufficient.
Important: Never stop warmup when you start sending campaigns. The best practice is to run warmup continuously to maintain reputation.
Warmup Best Practices
- Configure DNS first — SPF, DKIM, DMARC must be set up before starting warmup
- Start slow — 5 emails/day, increase by 3-5 per day
- Keep warmup running — Do not disable during campaigns
- Monitor your reputation — Check spam scores with Mail-Tester weekly
- Test inbox placement — Use GlockApps after warmup to verify you reach the inbox
See our warmup tools ranking for the complete list with detailed reviews.
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