Home › Microsoft
Microsoft 365 · Outlook · Azure
Prewarmed Microsoft inboxes
Licensed Exchange Online mailboxes, aged 30 days and warmed 21. From $6 an inbox in packs, or $50 for a tenant of 100.
Get Microsoft inboxes Work out how many →
Orders are placed on Warm Inboxes, run by the same team as this site.
Three names, two products
Microsoft 365 and Outlook inboxes are the same thing. Buyers search both, sellers quote both, and the mailbox underneath is a licensed Exchange Online account either way. Outlook the application is just software for reading mail, and Outlook.com is the free personal service, which is not sending infrastructure.
Azure — and Entra, which is the same directory under Microsoft's newer name — is the different product. Instead of buying mailboxes three at a time you get your own tenant holding 100 of them. Microsoft licenses that differently, which is why the cost per inbox drops by roughly ten times rather than a few percent.
The advantage nobody mentions
When Microsoft filters a message to junk, it writes a score and a few related notes into the message headers. Paste those into a header analyser and you get the actual reason — your copy, the sending server, or a record failing a check. Gmail tells you nothing of the kind.
That changes how fast you can fix things. On Google you watch reply rates fall and guess. On Microsoft you find out which of three problems you have, and one of them you can fix the same afternoon. It is a good reason to keep some volume on Microsoft even when your list is Google-weighted.
Microsoft is harder on new senders
It is stricter than Gmail with senders it does not recognise and it weights spam complaints heavily. In practice that means ramping more slowly, keeping bounces low, and expecting the Microsoft side of a fleet to take longer to come good than the Google side. Landing in Gmail while going to junk at Outlook is normal early on and does not mean the setup is broken.
It also means authentication has to be right from the first day rather than fixed later. Every domain we hand over arrives with SPF, DKIM, DMARC and MX published and checked, because three weeks of warming on a broken record is three weeks that did nothing.
Packs or a tenant
This is the only real decision on the Microsoft side, and it is about risk rather than price. Packs of three keep a failure contained: a domain goes, you lose three inboxes. A tenant is one flat price, and you choose how many mailboxes go in it — 25, 49 or 100. That is $2.00, $1.02 or $0.50 an inbox, and it is also how much of your fleet one unverified list can reach.
Under about 1,000 cold emails a day, buy packs — the saving is not worth the concentration. Above it, buy a tenant and run it properly: verified lists only, mailboxes started in batches of about twenty rather than all at once, and bounce rate checked daily for the first fortnight. The two are compared directly in Azure tenant vs Microsoft 365 packs.
Prewarmed Microsoft 365 inboxes
Licensed Microsoft 365 mailboxes for cold email, warmed on an aged .com with authentication configured. Delivered same day by Warm Inboxes.
View →Prewarmed Outlook inboxes
Prewarmed Outlook inboxes on licensed Microsoft 365 mailboxes, on an aged domain with authentication configured. Delivered same day.
View →Prewarmed Azure tenants
A dedicated prewarmed Azure tenant with 100 Exchange Online mailboxes. Volume infrastructure for agencies and high-send teams.
View →Prewarmed Entra tenants
Prewarmed Microsoft Entra ID tenants with 100 Exchange Online mailboxes. What changed from Azure AD, and why it does not affect sending.
View →Fresh Microsoft 365 inboxes
Brand new licensed Microsoft 365 mailboxes with authentication published. No aging and no warming — the cheapest way to build capacity ahead of time.
View →Fresh Azure tenants
A dedicated Azure tenant with 100 Exchange Online mailboxes, delivered unwarmed. The cheapest sending capacity there is, and the hardest to bring online.
View →Before you buy from anyone
Ask how many days the domain aged before its first send, how many days it sent real mail before handover, and what the replacement terms are in writing. The full version is in the buyer's guide.
Questions
What is the difference between Microsoft 365, Outlook and Azure inboxes?
Microsoft 365 and Outlook are the same thing under two names: licensed Exchange Online mailboxes sold in packs. An Azure tenant is your own directory holding 100 mailboxes, at a far lower cost per inbox and with one shared reputation.
Are these Outlook.com accounts?
No. Free personal accounts cannot use your own domain properly and will not hold up at volume. What you want is licensed Microsoft 365 with Exchange Online on a domain you control.
Why does Microsoft tell me more than Google does?
Microsoft writes a filtering score and related notes into the hidden part of the message. Paste it into a header analyser and you get the reason your mail was filtered. Gmail gives you nothing comparable.
Packs or an Azure tenant?
Under about 1,000 cold emails a day, packs. A failure stays contained to three inboxes. Above that a tenant is dramatically cheaper, and all 100 mailboxes share one reputation, so it rewards discipline and punishes a bad list fast.
Is Entra different from Azure AD?
Only the name and the interface. Microsoft renamed Azure Active Directory to Entra ID. Nothing about how your email lands changed.