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Prewarmed Microsoft 365 inboxes

Prewarmed Microsoft 365 inboxes for Outlook-heavy lists

Paid Microsoft 365 mailboxes on a domain aged 30 days and warmed 21, with the email records set up before you get it.

prewarmed.org is operated by the team behind Warm Inboxes (warminboxes.com) and Upscale B2B (upscaleb2b.com). Orders are fulfilled by Warm Inboxes.

ProviderMicrosoft 365, Exchange Online

Domain age when you get it30 days minimum

Warming21 days of real emails sent and received

DomainPrewarmed .com or .co, included

Email recordsSPF · DKIM · DMARC · MX already set

Suggested volume15 cold emails per inbox per day

You get itSame day, business days

Who this is for

Enterprise and mid-market sellers

The companies you are targeting run Microsoft. Sending from Google into a Microsoft-heavy file gives up placement you did not need to give up.

Teams that want to see why mail failed

Microsoft stamps its filtering verdict into the headers. It is the only major provider that tells you the reason.

Anyone diversifying off a single provider

A fleet entirely on one platform fails together. Splitting across two is the cheapest correlated-failure insurance there is.

The diagnostic advantage nobody mentions

When Microsoft sends a message to junk, it writes a score and a few related notes into the hidden part of the email. Paste that into a header analyser and you get the actual reason, not a guess. Gmail gives you nothing like it.

That changes how fast you can fix things. If you only send from Google, all you know is that fewer emails are landing. With Microsoft you find out whether it was something in your copy, a problem with the server you send from, or your records failing a check. One of those you can fix this afternoon.

Why a 60/40 split is the common answer

Most agencies sending a lot of cold email end up around 60 percent Google and 40 percent Microsoft, and they get there by measuring, not by guessing. The right split is whatever matches your list. You can work that out in minutes, and most teams never do.

There are two other benefits. One provider changing its rules cannot take out your whole operation, and when one of them cracks down you still have working inboxes while you adjust.

Authentication and sequencer connection

Microsoft has been shutting off the older, simpler way of logging in. Connect your sending tool using the modern method where it offers one. If your tool only supports the old way, check it still works before you build a campaign around it.

Every domain arrives with DMARC already set up. On a domain you only use for cold email, nothing else should ever be sending from it, which makes the strictest setting both safe and correct once the reports confirm it.

Pricing

Prewarmed Microsoft 365 · sold in packs of 3 · prewarmed domain included
Billing	Per inbox	Pack of 3
Monthly	$8	$24
2-Month	$7	$21
Quarterlybest value	$6	$18

Same day on business days. No refunds.

Order at Warm Inboxes →

Building capacity rather than launching? Fresh Microsoft 365 inboxes cost less and you warm them yourself.

Questions

Is this the same as the Azure tenant product?

No. These are individual paid mailboxes sold in packs. An Azure tenant is one account holding 100 mailboxes at a much lower cost per inbox, but all 100 share one reputation. See the comparison.

Will these work with my sequencer?

Yes. Use OAuth where available. Set per-inbox daily caps to your ramp figure, not the platform default.

Why send from Microsoft at all?

Because a meaningful share of B2B recipients are on Microsoft, and placement into those mailboxes is better from Microsoft infrastructure.

How is DMARC configured?

Published before handover. Read the reports for a fortnight before moving policy to enforcement.