When you manage many mailboxes or run your own sending system, choosing the right Email Warmup API is key to keeping deliverability stable. 

The challenge is that each provider offers a different level of control, automation, and reliability, so finding the right fit can feel confusing.

In this guide, you’ll see the 5 best Email Warmup API providers to look at today.

We’ll break down Warmforge, Warmy, Instantly, Mailreach, and Mailivery, and how each one lets you handle warmup through API access or automated workflows.

By the end, you’ll have a clear picture of how these tools compare and which one makes the most sense for your setup.

TL;DR: 5 Best Email Warmup APIs at a Glance

• Warmforge - Best email warm-up API for teams that need stable inbox placement, detailed warm-up diagnostics, and API-based automation for warming mailboxes at scale.‍
• Warmy - A strong email warm-up tool for teams that want Google Postmaster insights and broader domain-level deliverability data alongside warm-up activity.‍
• Instantly - Best for teams that want email warm-up and cold outreach in one platform, without managing a separate warm-up API or tool.‍
• Mailreach - Well-suited for email warm-up focused on natural sending behavior and sender reputation recovery, especially for struggling domains.‍
• Mailivery - Ideal email warm-up solution for agencies and SaaS teams that need to warm up a large number of mailboxes with flexible or unlimited inbox limits.

Connect the Warmforge API and keep your emails landing in the inbox without extra effort.

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What to Look For in an Email Warmup API

Short answer: judge an email warmup API on uptime, volume control, per-mailbox scale, pool quality, and placement data. Price comes last.

I have connected warmup APIs to three different sending setups. These are the eight things I check before I sign up.

• API reliability and uptime: Warmup only works if it runs every day without a gap. Find the status page and ask for the real uptime number.
• Real warmup control: You should be able to start, pause, and change daily volume from code. Ramp-up control matters most when you are repairing a domain you already burned.
• Clear docs and same-day access:" Check whether you can get an API key and make your first call today. Some providers make you book a sales call before they hand over access.
• Scale across mailboxes and domains: Ask whether warmup volume is per mailbox or shared across all of them. Shared limits look fine at 10 mailboxes and thin out fast at 100.
• Strong warmup network quality: Pool quality beats pool size. Ask what is inside the pool, and whether warmup activity runs in more than one language.
• Reputation tracking and placement data: Look for a reputation score per mailbox, placement tests across Google and Microsoft, and DNS, MX, and blacklist checks. Warmforge covers all three with Heat Score™, Inbox Placement Tests, and Health Checks.
• Pricing at your real volume: Do the math at the mailbox count you will hit in six months. At $25 per mailbox, 100 mailboxes costs $2,500 a month.
• Secure API access: Check the auth model before you connect live mailboxes. I look for scoped API keys, token-based auth, and the ability to revoke one key without breaking the rest.

5 Top Email Warmup API Providers (Discussed in Detail)

Go through the table below for a quick overview of all five email warmup API providers.

1. Warmforge

Warmforge is an email warmup and deliverability tool that also gives you an API to manage warmup directly inside your own system. 

It creates natural inbox activity using AI-written emails so your mailboxes build trust with email providers. 

It also offers placement tests and health checks, giving you a full view of how your mailboxes are performing. 

Warmforge works with Google Workspace and Microsoft 365, and you can start warming up as soon as you connect your accounts.

Key Email Warmup API Features

• AI-powered warmup that creates real inbox activity, not basic automated sends
  
  
• Always-on warmup to keep sending patterns stable as volume changes
  
  
• ESP-specific placement tests for Google Workspace and Microsoft 365
  
  
• Built-in DNS, MX, and blacklist checks to catch issues early
  
  
• Large, active warmup network that scales smoothly with your inboxes
  

Pricing

Warmup slots start at $10 per month (billed quarterly).

Each slot includes:

• Automated AI warmup
  
  
• One free placement test each month
  
  
• Full DNS, MX, and blacklist health checks
  

Placement test plans:

• Pro Plan: 100 tests per month for up to 50 mailboxes
  
  
• Growth Plan: Unlimited tests for up to 250 mailboxes
  

You can also book two 1:1 expert sessions for $500.

If you use Salesforge, Warmforge warmup is included for free.

Pros

• Stronger deliverability visibility with placement tests and health checks, which many warmup tools like Instantly and Mailery don’t combine in one place.
  
  
• API support makes it easier to plug warmup and deliverability checks into your own system, unlike tools that stay mostly UI-based.
  
  
• A large warmup network helps keep the mailbox reputation stable, even when scaling.
  
  
• Good for teams that want deeper deliverability insight, not just basic warmup.
  
  
• Cost advantage for Salesforge users, since warm-up is included for free.
  

Cons

• Not an outreach platform, so you still need another tool if you want a warm-up and sending in one place (like Instantly).

‍2. Warmy

Warmy is an email deliverability platform that includes a dedicated Email Warmup API for teams and products.

It prepares domains and IPs for outreach using AI-driven automation and Google Postmaster data, giving you clear visibility into how email providers see your sending behavior.

Warmy is built around deliverability insights.

It helps you avoid spam, promotions, and inbox placement issues in real time, and gives your team a shared dashboard to monitor reputation and performance. 

Key Email Warmup API Features 

• Email Warmup API to add automated warmup directly into your product or system
  
  
• API access for deliverability workflows, not just warmup actions
  
  
• Project and mailbox setup via API with quick onboarding
  
  
• API-driven warmup control without manual dashboard work
  
  
• Developer-friendly integration with ready-made interfaces and clear documentation
  
  
• API support for scaling warmup across many accounts
  

Pricing

Warmy does not share its pricing publicly.

There is no fixed or self-serve pricing listed on the website.

Warmy mentions B2B, B2C, and custom plans, but exact costs are only provided after contacting their sales team or booking a demo.

A 7-day free trial is available, but pricing details are not disclosed upfront.

This means you’ll need to speak with their team to understand the actual cost.

Pros

• Strong focus on improving inbox placement using AI and Google Postmaster data
  
  
• Real-time insights make it easy to find and fix deliverability issues fast
  
  
• API is flexible and works well for SaaS tools wanting a built-in warmup
  
  
• Good for both B2B and B2C senders because of separate warmup networks
  
  
• Dedicated experts available to help with deliverability guidance
  

Cons

• API onboarding is not instant, which slows down developers who want to integrate quickly.
  
  
• Requires ongoing dashboard monitoring, unlike simpler “set and forget” warmup tools.‍

• Not optimized for pure warmup-only use cases, as deliverability tooling is tightly bundled.

3. Instantly

Instantly is an outreach platform that also includes unlimited email warm-up.

It’s built for teams that want a warm-up and sending in one place, instead of using separate tools. 

You can add as many email accounts as you want, warm them all at once, and run your outreach from the same dashboard. 

Instantly is also known for being easy to use, fast to set up, and friendly for scaling.

Key Email Warmup API Features 

• API and webhooks to connect warmup with external systems
  
  
• Programmatic access to warmup status and account data
  
  
• Automation support alongside outreach workflows
  
  
• API-based integrations with CRMs and third-party tools
  
  
• Scalable API usage for managing multiple email accounts
  

Pricing

Instantly keeps pricing simple with warmup included in every plan:

• Growth - $30/mo: Unlimited warmup + 5,000 emails/month
  
  
• Hypergrowth - $77.6/mo: Unlimited warmup + 100,000 emails/month
  
  
• Light Speed - $286.3/mo: Higher sending limits and advanced features
  
  
• Enterprise - Custom: More volume, a deliverability network, and an account manager
  

You can start for free with no credit card.

Pros

• Easy for teams that want warm-up and outreach together instead of using two tools
  
  
• Unlimited warmup makes it cost-effective when you manage many mailboxes
  
  
• API and webhooks give flexibility for custom workflows
  
  
• Very simple setup, even when adding a lot of accounts
  
  
• Good option if you want sending, tracking, and warm-up in one platform
  

Cons

• Warmup is tied to the outreach platform, so it’s not ideal if you only want warmup
  
  
• Not as deliverability-focused as tools built purely for warmup and inbox health
  
  
• If you prefer deep deliverability testing or mailbox diagnostics, other tools offer more detail
  

‍4. Mailreach

Mailreach is a deliverability tool that focuses on warming up your mailbox and improving your sender reputation. 

It also gives you an Email Warmup API so you can add warmup directly into your own workflow or platform. 

Mailreach is built for teams that want stronger inbox placement, smoother ramp-up control, and a warm-up process that feels natural and conversational instead of robotic.

Key Email Warmup API Features 

• Dedicated Email Warmup API built specifically for deliverability automation
  
  
• API control over warmup pace and volume
  
  
• Real-time reputation and performance data via API
  
  
• Webhook and alert support for reputation score changes
  
  
• API compatibility across major ESPs (Google, Microsoft, others)
  

Pricing

Mailreach keeps pricing simple and mailbox-based:

• $25 per mailbox/month
  
  
• Includes 20 spam-test credits, inbox and domain health checks, 100 warmup emails/day, and reputation tracking

• Custom pricing is available for agencies or teams warming multiple mailboxes.

Pros

• Mailreach builds trust faster because its warmup uses real, natural conversations, not basic one-way emails like many other tools.
  
  
• You get more control over warmup speed, which helps when fixing a damaged domain, something many tools don’t let you fine-tune.
  
  
• Reputation tracking is clearer than most competitors because it shows how each provider (Google, Microsoft, etc.) views your mailbox.
  
  
• Warmup emails stay hidden, so your inbox doesn’t get messy when you're handling many accounts.
  

Cons

• Pricing is per mailbox, so costs rise quickly if you manage a lot of accounts.
  
  
• It’s not an outreach tool, so you still need another platform for sending campaigns.
  
  
• Warmup caps (around 100 emails/day) make scaling slower compared to tools with heavier volumes.
  
  
• API setup requires more steps, while some tools offer quicker plug-and-play access.

‍5. Mailivery

Mailivery is an email warmup and deliverability tool that uses AI plus a large peer-to-peer network to create real interactions in your inbox. 

These interactions help your emails avoid spam filters and land in the primary inbox more often. 

It’s built for teams, agencies, and SaaS platforms that want warmup at scale, and its API lets you automate mailbox connections, warmup settings, monitoring, and onboarding inside your own system. 

Mailivery also includes blacklist monitoring, email verification, and customizable sending behavior to keep your reputation stable.

Key Email Warmup API Features 

• Full warmup control through API (start, pause, adjust volume, ramp-up)
  
  
• API support for unlimited mailboxes under one account
  
  
• Deliverability metrics and health data via API
  
  
• Webhook notifications for warmup and mailbox events
  
  
• Developer-friendly REST API designed for SaaS and high-volume teams

Pricing

Mailivery offers simple plans with unlimited mailboxes and shared daily warmup limits:

• Starters - $29/mo: Up to 100 warmup emails/day
  
  
• Professional - $79/mo: Up to 600 warmup emails/day
  
  
• Business - $199/mo: Up to 2,000 warmup emails/day
  
  
• All plans include blacklist monitoring, analytics, AI content, and peer-to-peer interactions
  
  
• 7-day free trial available
  

Pros

• Mailivery becomes more cost-effective than many tools because it lets you warm unlimited mailboxes, while most competitors charge per inbox.
  
  
• Its peer-to-peer warmup with real accounts makes the interactions look more natural than tools that use basic bot emails.
  
  
• The customizable sending behavior gives more control compared to tools that lock you into fixed warmup schedules.
  
  
• Strong deliverability add-ons like blacklist monitoring and email verification give it an edge over warmup-only tools.
  
  
• The API is built for large teams, agencies, and SaaS, making it easier to manage many inboxes from one system.
  

Cons

• Warmup volume is shared across all inboxes, so each mailbox gets less warmup as you add more accounts, unlike tools that give fixed per-mailbox volume.
  
  
• It doesn’t include outreach, so you still need a separate sending tool if you want campaigns and warmup together.
  
  
• API access requires a call first, not instant signup, which slows down onboarding.
  
  
• Plans may feel heavy for small users who only need to warm a few mailboxes, since Mailivery is designed more for scale.
  

‍How to Choose the Right Email Warmup API

Picking the right Email Warmup API mostly depends on how you work and how many mailboxes you manage.

Here’s a simple way to decide:

Conclusion

Choosing the right Email Warmup API comes down to what you need: automation, deliverability insight, scale, or an all-in-one outreach setup.

Each tool in this list solves the warmup problem differently. 

• Warmforge focuses on deliverability, warmup, placement tests, DNS/MX checks, blacklist monitoring, and an easy API.
   
• Warmy adds Postmaster insights and broader deliverability reporting for mixed B2B/B2C sending.
  ‍
• Instantly is the right fit if you want warm-up and outbound campaigns in the same platform.
  ‍
• Mailreach is strong when you need natural warmup behavior and detailed provider-level reputation tracking.
  ‍
• Mailivery works well for agencies and SaaS platforms that need unlimited mailboxes and API-driven warmup across large setups.

If your main goal is to send at scale while keeping inbox placement stable, choose Warmforge.

It keeps deliverability predictable and makes warmup easy to automate, even when you’re managing multiple domains or mailboxes.

Plug in the Warmforge API, automate your warmup, and keep your emails landing in the inbox every time.

FAQs

1. What is an email warmup API?

An email warmup API lets you start, pause, and monitor mailbox warmup from your own code instead of a dashboard. Most also return reputation and placement data you can show inside your own app.

2. Do I actually need a warmup API, or is a dashboard enough?

Most senders do not. Under 20 mailboxes, the dashboard is faster than building anything.

The API pays off when mailboxes get created automatically, like an agency onboarding a client every week.

3. How long does email warmup take before I can send cold email?

Two to four weeks for a brand new mailbox. I do not send a real campaign before day 14.

You can skip the wait with pre-warmed mailboxes from Primeforge or Infraforge. Warmforge keeps them warm after that, including IMAP and SMTP mailboxes from Mailforge.

4. How much does an email warmup API cost?

Expect $9 to $29 per mailbox per month, or a flat plan from $29 for unlimited mailboxes.

Here is the spread from this list:

• Warmforge: $9 per mailbox slot per month, billed annually
• MailReach: $25 per mailbox per month
• Mailivery: $29 to $199 per month, unlimited mailboxes, shared daily warmup volume
• Instantly: warmup included from $30 per month
• Warmy: no public pricing, quoted after a sales call

5. Is Warmforge warmup really free with Salesforge?

Yes. Every Salesforge plan includes unlimited Warmforge warmup slots at no extra cost, on Pro at $48 per month and Growth at $96 per month.

Standalone Warmforge is $9 per mailbox slot per month, billed annually.

6. Does warmup on its own fix deliverability?

No. Warmup builds sender reputation, but it cannot save a bad list or a domain with broken DNS.

You still need SPF, DKIM, and DMARC set up correctly, validated contacts, sender rotation across mailboxes, and text-only emails.