5 Best Prewarmed MS365 Mailboxes For Cold Outreach (2025)

Setting up Microsoft 365 inboxes for cold outreach is hard. You have to buy domains, configure SPF and DKIM, wait weeks to warm up the inboxes, and still, your emails might go to spam.

That’s why many people now use pre-warmed Microsoft 365 inboxes. These are Outlook accounts that already have sending history, proper DNS setup, and are ready to send emails right away.

In this blog, we’ll show you the 5 best providers of pre-warmed MS365 mailboxes. These services help you skip setup delays and launch cold email campaigns in hours.

Whether you're a solo founder, agency, or B2B team, these mailbox providers make cold outreach faster, safer, and more reliable.

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What Are Prewarmed Microsoft 365 Mailboxes?

Prewarmed Microsoft 365 mailboxes are Outlook email accounts that have already been used to send and receive emails before you get them. 

They are not brand new. These inboxes have a sending history that makes them look trustworthy to Microsoft.

The DNS settings like SPF, DKIM, and DMARC are already set up. This helps your emails avoid spam folders and reach the inbox.

Because the warm-up is already done, you don’t have to wait weeks before using them. You can start sending cold emails right away.

In short, a prewarmed Microsoft 365 mailbox is ready to use on day one, with no technical setup or warm-up delay.

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How We Chose the 5 Best Prewarmed Microsoft 365 Mailboxes

We didn’t just list random providers. We tested and reviewed each one based on what really matters for cold outreach. 

Here’s what we looked for when choosing the best prewarmed Microsoft 365 mailboxes:

• The inbox must already have real email activity, not just a fresh account created yesterday. It should have sent and received emails to build trust with Microsoft.
  
  
• SPF, DKIM, and DMARC must be properly set up, so your emails pass authentication checks and don’t land in spam.
  
  
• It must be a real Microsoft 365 account, not just a random inbox or SMTP account with no admin control.
  
  
• Setup should be fast and smooth, ideally within minutes or hours, not days.
  
  
• The domain and IP must be clean and unused, so you’re not stuck with a flagged or recycled domain.
  
  
• The pricing must be fair for scaling, especially if you're an agency or sending from multiple inboxes.

We applied all of these checks to make sure you only see the most reliable pre-warmed Microsoft 365 mailboxes in this list.

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5 Best Pre-Warmed Microsoft 365 Mailboxes: Quick Look

1. Primeforge – Pre-warmed Microsoft 365 inboxes with dedicated IPs, clean domains, and automatic DNS setup. Built for serious cold outreach teams.
   
   
2. Zapmail – Pre-warmed Microsoft 365 mailboxes with over 12 weeks of warm-up history and instant OAuth access for smooth tool integration.
   
   
3. Smartlead (SmartSenders) – Fully prewarmed Microsoft 365 mailboxes delivered in 30–40 mins, integrated directly into a cold outreach platform.
   
   
4. LiteMail – Simple, affordable pre-warmed Outlook mailboxes with basic DNS setup and quick delivery.
   
   
5. InboxKit – Microsoft 365 mailboxes with full admin access, MFA enabled, Cloudflare Enterprise DNS, and SmartSenders integration.
   
   

1. Primeforge

Primeforge is a cold email infrastructure platform made specifically for cold email. It gives you prewarmed Microsoft 365 and Google Workspace mailboxes that are ready to use within 30 minutes. 

It helps people send cold emails without worrying about technical setup, DNS records, or spam issues. You don’t need to deal with Microsoft directly, Primeforge takes care of everything for you.

It gives you full access to clean, warmed mailboxes with US-based IP addresses, fully configured DNS (SPF, DKIM, DMARC), and smart deliverability features like profile GIFs.

Key Features of Primeforge:

• The setup is fully automated, including domain verification, SPF, DKIM, and DMARC, so you don’t need technical knowledge to get started.
  
  
• It offers real Microsoft 365 mailboxes with complete domain and mailbox ownership, not just shared logins or SMTP ports.
  
  
• The mailboxes are ready in 30 minutes, much faster than waiting 24+ hours when setting up Microsoft or Google accounts manually.
  
  
• It uses US-based IP addresses for better trust and inbox placement, especially in North America.
  
  
• The tool works with any cold email platform, like Smartlead, Instantly, Lemlist, or Salesforge, without extra configuration.
  
  
• The system is built to match the email provider of your prospects, improving inbox placement through a technique called ESP matching.
  

Pros and Cons of Primeforge:

Primeforge Pricing:

Primeforge pricing is flexible, but the cost depends on how many mailbox “slots” you purchase and whether you choose monthly or yearly billing:

• Monthly: $4.5 per mailbox/month (for 10 mailboxes minimum)
  
  
• Yearly (billed annually): $3.5 per mailbox/month (includes 2 months free)
  
  

For example, If you need 10 mailboxes, you’ll pay $45/month on the monthly plan or $35/month on the yearly plan.

Every subscription includes:

• Full Microsoft 365 or Google Workspace mailbox
  
  
• Automated DNS setup (SPF, DKIM, DMARC)
  
  
• Ongoing maintenance and hosting
  
  
• Support and access to Primeforge API
  
  
• Mailbox management features

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2. Smartlead

Smartlead is a cold outreach platform that now offers fully prewarmed Microsoft 365 and Gmail mailboxes through its feature called SmartSenders. 

These mailboxes are verified, tested, and inbox-ready, so you can start sending cold emails the same day without going through the typical warm-up phase.

Everything is handled within the Smartlead dashboard: from domain selection and mailbox creation to inbox customization. 

The prewarmed mailboxes are typically delivered within 30–40 minutes, with full SPF, DKIM, and DMARC authentication already in place.

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Key Features of Smartlead:

• Smartlead delivers fully prewarmed Microsoft 365 or Gmail mailboxes within 30–40 minutes, so you can start sending cold emails right away.
  
  
• It sets up SPF, DKIM, and DMARC automatically, removing the need for any manual DNS or technical setup.
  
  
• The tool allows you to choose from pre-verified generic domains, each of which can host up to 3 warm mailboxes.
  
  
• It works with both Microsoft Outlook and Gmail, giving flexibility for teams targeting different platforms.
  
  
• It supports inbox testing across major providers like Outlook, Gmail, and Yahoo to ensure high deliverability.
  
  

Pros and Cons of Smartlead:

Smartlead Pricing:

Smartlead offers flat pricing for mailboxes and domains:

• Mailbox: $9/month
  
  
• Domain: $18/year
  

Each domain supports 3 mailboxes. For example, if you need 6 mailboxes, you’ll pay $54 total: 6 mailboxes × $9 + 2 domains × $18 (annualized monthly).

Every plan includes:

• Prewarmed mailbox with full inbox readiness
  
  
• Domain with full SPF, DKIM, and DMARC setup
  
  
• Full access to Smartlead outreach platform
  

Campaign management, tracking, and inbox rotation

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3. Zapmail

Zapmail is a cold email infrastructure tool that provides prewarmed Google Workspace and Microsoft 365 mailboxes, optimized for deliverability from day one.

It automates everything from domain setup to DNS configuration (SPF, DKIM, DMARC) and offers fast deployment through OAuth connections, eliminating the need for SMTP or app passwords.

Key Features of Zapmail:

• The mailboxes are ready instantly, with 12+ weeks of warm-up history, so you can start sending from day one without using any warm-up tools.
  
  
• The setup is fully automated, including domain provisioning, DNS configuration (SPF, DKIM, DMARC), and OAuth-based connections to outreach tools.
  
  
• The platform offers workspace-level isolation, where each domain gets its own workspace and admin access for reduced ban risk.
  
  
• It provides AI tools like Instant Domain Genie and Smart Mailbox Namer, allowing you to generate branded domains and clean mailbox handles in seconds.
  

Pros and Cons of Zapmail:

Zapmail Pricing:

I. Standard Microsoft 365 / Google Mailboxes

• Starter Plan: $39/month, 10 mailboxes included
  
  
• Growth Plan (Popular): $99/month, 30 mailboxes included
  
  
• Pro Plan: $299/month, 100 mailboxes included
  
  
• Additional Mailboxes:
  – $3.50/mailbox (Starter)
  – $3.25/mailbox (Growth)
  – $3.00/mailbox (Pro)
  
  
• All plans include US/EU IPs, support, and instant setup
  
  
• API access included in Pro plan

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II. Pre-Warmed Mailboxes

• Starter: $39 first month → $24/month, 3 mailboxes + 1 domain, extra mailboxes: $8 each/month
  
  
• Growth: $149 first month → $84/month, 12 mailboxes + 4 domains, extra mailboxes: $7 each/month
  
  
• Pro: $339 first month → $180/month, 30 mailboxes + 10 domains, extra mailboxes: $6 each/month
  
  
• Extra domain: $15/year

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III. Domain Pricing

• Bring your own domain or buy from Zapmail
  
  
• .com domains start at $13/year

Related Read:5 Zapmail Alternatives & Competitors Used By Top Consultants

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4. LiteMail

LiteMail is a budget-friendly cold email infrastructure platform that offers prewarmed Google Workspace and Microsoft 365 mailboxes. 

It automates the entire setup, including mailbox creation, domain provisioning, and DNS configuration (SPF, DKIM, DMARC), and is ready to use in under 30 minutes. 

You get official Google or Microsoft mailboxes, not just SMTP relays, with full admin access.

The system uses US- and EU-based IPs, enforces workspace-level isolation, and supports OAuth-based integration with over 50 cold outreach tools like Smartlead, Instantly, and Lemlist.

Key Features of LiteMail:

• The platform provisions real Google Workspace and Microsoft 365 mailboxes through official APIs with no manual steps or SMTP setups.
  
  
• The setup is fully automated, including domain creation, SPF, DKIM, DMARC, and profile personalization (name, image, etc.).
  
  
• The mailboxes are ready in 30 minutes, and come with 4–12 weeks of warm-up history for instant cold outreach.
  
  
• Each domain gets its own dedicated workspace and admin panel, reducing the risk of cross-domain bans.
  
  
• LiteMail supports auto-reply detection, inbox tracking, follow-up reminders, and smart alerts for replies, clicks, or opens.
  

Pros and Cons of LiteMail:

LiteMail Pricing:

I. Pre-Warmed Mailbox Plans:

• Starter Plan: $39/month (first month $54), includes 5 prewarmed Google or Microsoft mailboxes + 1 domain → Extra mailboxes: $8/month
  
  
• Growth Plan: $99/month (first month $159), includes 13 prewarmed mailboxes + 4 domains → Extra mailboxes: $7/month
  
  
• Pro Plan: $199/month (first month $349), includes 30 prewarmed mailboxes + 10 domains → Extra mailboxes: $6/month
  
  
• Extra Domains: $15/year
  
  

II. Microsoft 365 Mailbox-Only Pricing:

• Starter (1–10 inboxes): $3.50/inbox/month
  
  
• Growth (11–30 inboxes): $3.25/inbox/month
  
  
• Pro (30+ inboxes): $3.00/inbox/month
  
  
• Domains: $15/year

All Microsoft 365 mailbox plans include <12h delivery, US/EU IPs, DNS config, and support.

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5. InboxKit

InboxKit is a trusted cold email infrastructure provider offered through Smartlead, giving you prewarmed Google Workspace and Microsoft 365 (Outlook) mailboxes with full admin access.

With pre-configured SPF, DKIM, and DMARC, the setup is production-ready within ~48 hours.

InboxKit is tightly integrated with SmartSenders, so Smartlead users get plug-and-play deliverability infrastructure without needing to touch DNS records manually.

Key Features of InboxKit:

• It provides prewarmed Google Workspace and Microsoft 365 mailboxes, ready for cold outreach, with full control via the respective admin dashboards.
  
  
• LiteMail automates the entire setup, including mailbox creation, domain provisioning, and DNS authentication (SPF, DKIM, DMARC), eliminating technical complexity.
  
  
• It uses Enterprise-grade Cloudflare DNS and enables MFA by default, ensuring high security and strong anti-spam compliance.
  
  
• The platform provisions each domain in a unique Google Workspace or Microsoft 365 tenant, isolating sender reputation and reducing the risk of bans or shared blacklists.
  
  
• It allows 1–5 mailboxes per domain, giving flexibility while keeping domain reputation protected.
  

Pros and Cons of InboxKit:

InboxKit Pricing:

• Mailboxes: $3.5/month per Google or Outlook mailbox
  
  
• Domains: $13/year per domain
  
  
• Included in Pricing:
  
  • Pre-configured SPF, DKIM, DMARC
    
    
  • Full admin access
    
    
  • Cloudflare DNS & MFA
    
    
  • SmartSenders compatibility
    
    
  • Workspace or tenant isolation
    

Setup time: ~48 hours after payment

Warm-up compatible and secure by default

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Which Prewarmed MS365 Mailboxes For Cold Outreach Should You Choose?

If you’re sending cold emails, using prewarmed Microsoft 365 mailboxes can save you a ton of time and boost your deliverability. But not all tools are the same.

• If you're just getting started or on a budget, LiteMail and InboxKit offer affordable and simple setups.
  
  
• For users already on Smartlead, SmartSenders, or InboxKit are great plug-and-play options.
  
  
• If you need fast deployment, clean infrastructure, and support for high-volume outreach, Zapmail offers powerful automation.
  
  
• But if you want full control, premium IPs, and a rock-solid foundation for cold outreach, Primeforge is the top choice.
  

It gives you prewarmed Microsoft 365 mailboxes with your own domain, clean US IPs, and setup in just 30 minutes. 

Sign up with Primeforge now!

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