--- title: "Prewarmed Microsoft 365 Inboxes for Cold Email" description: "Genuine Microsoft 365 inboxes for cold email, prewarmed and sending the day they land, with free .com domains, DNS verified by hand, and bulk MS365 pricing." url: https://warminboxes.com/microsoft-365-inboxes breadcrumb: "Home > Microsoft 365 Inboxes" --- [WarmInboxes.com](https://warminboxes.com/) [Offer](https://warminboxes.com/offer) [Free Leads](https://warminboxes.com/leads) [Free Tools](https://warminboxes.com/deliverability-tools) [Blog](https://warminboxes.com/blog) [Reviews](https://warminboxes.com/reviews) [Home](https://warminboxes.com/) › Microsoft 365 Inboxes Microsoft 365 Cold Email Infrastructure # Prewarmed Microsoft 365 Inboxes Built to Reach Outlook Prospects Real Outlook business accounts on prewarmed .com domains, DNS human-verified, delivered within 48 to 72 hours and sending on arrival. The matching infrastructure for the enterprise half of your lead list that lives on Microsoft. Genuine Microsoft 365 business accounts, officially licensed, never grey-market Free prewarmed .com domains included, already forwarding to your site SPF, DKIM, DMARC configured and human-verified before delivery Bulk MS365 tiers for agencies and enterprise volume senders The same infrastructure behind 1,000,000+ cold emails every month at 4%+ reply rates. Built by operators for their own agency first, sold to you second. [Get Prewarmed Inboxes](https://app.warminboxes.com/signup) Free .com domains included Delivered in 48 to 72 hours No contracts, cancel anytime ## Why Microsoft 365 Inboxes for Cold Email? Enterprise B2B runs on Microsoft. Finance, insurance, manufacturing, legal, healthcare: the buyers with budgets are overwhelmingly behind Outlook and Exchange Online, and Microsoft filters strangers hard. 1 ### Your enterprise prospects live on Microsoft Run any enterprise-heavy list through our free ESP Segmenter and watch the Microsoft share. In our own campaigns, sending to Outlook-hosted prospects from matching Microsoft infrastructure meets less filtering friction than sending to them from elsewhere. 2 ### Microsoft punishes unfamiliar senders hardest Outlook’s SCL scoring junks new, unknown senders faster than any other filter, which makes warmed history worth more on Microsoft than anywhere. A prewarmed M365 inbox arrives already familiar, the single biggest head start you can buy on this platform. 3 ### Exchange admin is genuinely painful, so we do it Tenant setup, Exchange Online configuration, authenticated SMTP or OAuth, connectors, and DNS records that break silently: Microsoft setup is where DIY infrastructure projects go to die. We handle all of it and hand-verify every record before your CSV ships. 4 ### Isolated tenants, never shared Cheap MS365 resellers stack customers into shared tenants where one bad sender poisons everyone. Every WarmInboxes customer gets isolated infrastructure, so your reputation is only ever a product of your own sending. ## What Working With Us Actually Saves You ### Lower cost than DIY, and free domains Free prewarmed .com domains with every order save $12 to $20 each before counting warmup time. Bulk tiers cut the per-inbox rate at volume, quarterly and yearly billing cut it again, and fresh inboxes on branded domains run a fraction per send when you scale. ### Weeks of Microsoft-grade warmup, skipped Fresh Microsoft accounts often need the most patient warmup in cold email because SCL filtering distrusts new senders. Prewarmed M365 inboxes carry that history already, so you send the day they land instead of babysitting a ramp for three weeks. ### Operators who know Microsoft’s quirks SCL scores, connector limits, throttling policies, the Outlook-specific traps: our team sends 1M+ cold emails a month across Google and Microsoft and supports you on WhatsApp 24/7. When something breaks mid-campaign, an operator works the fix with you. ### The free operating kit on top 55 free deliverability tools including an Outlook SCL Analyzer built for exactly this platform, a free B2B leads database of 999 lists, expert playbooks, and 101 guides. The full stack our agency runs on, included. ## The 3-Step Play That Keeps You Sending Most providers hand you inboxes and hope. We give you the operating system we run our own 1M+ sends a month on. 1 ### Launch with prewarmed inboxes Free .com domains, already warmed. Delivered within 48 to 72 hours and sending the day they land. Plug the CSV into your sequencer and go. 2 ### Scale with fresh inboxes on branded domains Once the campaign is booking meetings, layer in fresh inboxes at a fraction of the cost per send and let them warm behind live sending. 3 ### Recover in one message when infra burns Domains get flagged, that is the sport. One WhatsApp message gets the cause diagnosed with you, and more prewarmed inboxes ordered if you need them. ## More Than Inboxes: The Free Stack That Comes With Working With Us We made every internal tool our agency's GTM engineers use public and free. Customers get infrastructure plus the whole operating kit. ### 55 free deliverability tools Checkers for SPF, DKIM, DMARC, MTA-STS, blacklists, spam copy, CSV cleaning, inbox planning, and more. No account needed. [Browse the tools](https://warminboxes.com/deliverability-tools) ### Free B2B leads database Downloadable lead lists by industry and geography, hundreds of thousands of companies, emailed to you free. [Get free leads](https://warminboxes.com/leads) ### Playbooks + WhatsApp operators Expert deliverability playbooks, 101 guides, and 24/7 WhatsApp support from people who send cold email daily. [Read the playbooks](https://warminboxes.com/playbooks) New to this? Here is what ordering actually involves. - 1Create an accountFree, no card - 2Pick a packagePrewarmed or fresh - 3We build it48–72h, DNS configured - 4Plug in and sendConnected to your tool [How it works, in full](https://warminboxes.com/how-it-works) ## Choose Your Infrastructure Launch with prewarmed inboxes on free domains, then scale sending volume with fresh inboxes on your own branded domains. Prewarmed Inboxes (Free Domains + No Warmup Wait) Fresh Inboxes (Built for you + 21 day warmup) Skip 21 Day warmup wait. Ready-to-use inboxes with a free prewarmed .COM/.CO domain. Monthly Save 12% 2-Month Save 25% Quarterly ### Microsoft Inboxes (FREE Prewarmed .COM/.CO) 3 Ready-to-use Microsoft inboxes with a free prewarmed domain - no warmup period required. $6 /inbox/month Paid quarterly [Order Now](https://app.warminboxes.com) MOST POPULAR ### Google Inboxes (FREE Prewarmed .COM/.CO) 3 Ready-to-use Google inboxes with a free prewarmed domain - no warmup period required. $6 /inbox/month Paid quarterly [Order Now](https://app.warminboxes.com) ### Azure Inboxes (FREE Prewarmed .COM/.CO) 100 inboxes per tenant, free prewarmed domain, no warmup needed. $50 per tenant per month. $0.50 /inbox/month Paid quarterly [Order Now](https://app.warminboxes.com) On a budget? Prewarmed inboxes on lower-cost domain extensions from $4.5/inbox. [Message us](https://api.whatsapp.com/send/?phone=19047362539&text=Hey%2C%20I%20need%20WarmInboxes&type=phone_number&app_absent=0) ### Calculate What You Need [Calculate by volume Sends per day](https://warminboxes.com/calculator)[Calculate by recipient ESP Maximise deliverability](https://warminboxes.com/esp-calculator) ### Talk to 24/7 support [Contact Support on WhatsApp](https://api.whatsapp.com/send/?phone=19047362539&text=Hey%2C%20I%20need%20WarmInboxes&type=phone_number&app_absent=0) ## Common Questions Everything you need before you order. Are these real Microsoft 365 accounts? Yes. Every inbox is a genuine, officially licensed Microsoft 365 business account, never cracked, farmed, or resold from grey markets. You get full admin access and ownership, with customers isolated from each other so nobody else’s sending can ever touch your reputation. What is the difference between Outlook, Office 365, and MS365 inboxes? Naming only. Office 365 was rebranded Microsoft 365 in 2020, Outlook is the mailbox interface, and MS365/M365 are shorthand. Whichever term you searched, the product is the same: Exchange Online business mailboxes on your sending domains, which is exactly what we deliver prewarmed. Why do my cold emails go to Outlook junk from other providers? Usually SCL scoring: Microsoft assigns every inbound message a Spam Confidence Level, and unfamiliar senders with thin history score badly even with perfect DNS. Warmed Microsoft-native infrastructure attacks the problem at the root, and our free Outlook SCL Analyzer decodes the headers so you can see exactly why a message was junked. Do M365 inboxes work with Instantly, Smartlead, and other sequencers? Yes. Inboxes ship as a CSV pre-formatted for Instantly, Smartlead, EmailBison, ManyReach, Apollo, and any tool supporting IMAP/SMTP or OAuth. Plug in and send the day they land. Should I buy Google Workspace or Microsoft 365 inboxes? Match your list. Segment it by receiving provider first: tech and startup lists skew Google-hosted, enterprise and regulated industries skew Microsoft. Serious volume senders run both and route campaigns by recipient provider, which is why we are the rare provider offering Google, Microsoft 365, and Azure under one roof. What about bulk Microsoft 365 inboxes for agencies? Bulk tiers drop the per-inbox price at 30 and 100 inboxes with further cuts on quarterly and yearly billing. Agencies get per-client isolation, so one client’s campaign can never contaminate another’s infrastructure, and fast deployments keep client pipelines moving when domains burn. ## Order Today, Send Within 72 Hours Free prewarmed .com domain with every order. Delivered in 48 to 72 hours, human-verified DNS, built for warm deliverability. [Get Prewarmed & Fresh Inboxes](https://app.warminboxes.com/signup) No contracts Cancel anytime Delivered in 48 to 72 hours Also available: [Google Workspace inboxes](https://warminboxes.com/google-workspace-inboxes) · [Azure inboxes](https://warminboxes.com/azure-inboxes) ## Prewarmed & Fresh Inboxes Google, Microsoft 365 and Azure inboxes with free prewarmed domains and DNS configured before you log in. Prewarmed inboxes send the day they land; every order is delivered within 48 to 72 hours. [Get Prewarmed & Fresh Inboxes](https://app.warminboxes.com) More from WarmInboxes [Google Workspace Inboxes](https://warminboxes.com/google-workspace-inboxes)[Microsoft 365 Inboxes](https://warminboxes.com/microsoft-365-inboxes)[Azure Inboxes](https://warminboxes.com/azure-inboxes)[Deliverability](https://warminboxes.com/deliverability)[Terms of Service](https://warminboxes.com/terms)[Privacy Policy](https://warminboxes.com/privacy)[Developers](https://warminboxes.com/developers)[For AI Agents](https://warminboxes.com/for-ai)[Inboxes for Instantly](https://warminboxes.com/instantly-inboxes)[Inboxes for PlusVibe](https://warminboxes.com/plusvibe-inboxes)[Inboxes for Smartlead](https://warminboxes.com/smartlead-inboxes)[Inboxes for EmailBison](https://warminboxes.com/emailbison-inboxes)[Inboxes for Apollo](https://warminboxes.com/apollo-inboxes)[Inboxes for ManyReach](https://warminboxes.com/manyreach-inboxes)[Inboxes for Claude](https://warminboxes.com/claude-inboxes)[Inboxes for ChatGPT](https://warminboxes.com/chatgpt-inboxes)[Inboxes for Grok](https://warminboxes.com/grok-inboxes)[About](https://warminboxes.com/about)[Huzayfa Majeed](https://warminboxes.com/authors/huzayfa-majeed)[How it works](https://warminboxes.com/how-it-works)[Deliverability Hub](https://warminboxes.com/deliverability-hub)[Studies](https://warminboxes.com/research)[Placement Test Log](https://warminboxes.com/research/inbox-placement-log)[Top-Level Domains](https://warminboxes.com/research/google-sender-reputation)[SURBL Study](https://warminboxes.com/research/surbl-blocklist-study)[Playbooks](https://warminboxes.com/playbooks)[Calculator](https://warminboxes.com/calculator)[Consultation](https://warminboxes.com/consultation)[Affiliate Program](https://warminboxes.com/affiliate)[Tool demos](https://warminboxes.com/videos)[Testimonials](https://warminboxes.com/testimonials)[Reddit Reviews](https://warminboxes.com/reddit)[Prewarmed on Reddit](https://warminboxes.com/prewarmed/reddit)[Inboxes on Reddit](https://warminboxes.com/inboxes/reddit)[Revenue Boost](https://warminboxes.com/revenueboost)[MailFirst](https://warminboxes.com/mailfirst)[Agency Advanta](https://warminboxes.com/agencyadvanta)[Liquid Syntax Guide](https://warminboxes.com/playbooks/liquid-syntax-guide)[The SPAM Plague](https://warminboxes.com/playbooks/spam-plague-segmentation-playbook)[Inboxing Playbook](https://warminboxes.com/inboxing-playbook)[Data Ops Hub](https://warminboxes.com/hub/data-ops)[Agency Hub](https://warminboxes.com/hub/cold-email-agency) Contact [WhatsApp +1 904 736 2539](https://api.whatsapp.com/send/?phone=19047362539&text=Hey%2C%20I%20need%20WarmInboxes&type=phone_number&app_absent=0) · [support@warminboxes.com](mailto:support@warminboxes.com) · Pembroke Pines, FL 33024, USA