Warm Inboxes
Prewarmed Google and Microsoft inboxes with free domains, ready to send cold email on day one.
From $3/inbox/mo
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Bottom line
Cold email sending infrastructure: prewarmed Google, Microsoft 365 and Azure inboxes on free domains that can send the day you buy them, and cheaper fresh inboxes on your own domains for scaling. Fresh inboxes start at $3 a month and prewarmed ones at $8 a month each.
Stands out for: Prewarmed inboxes skip the two to three week warmup, so a recruiting desk can start a business development campaign the same day or swap in fresh senders when a domain burns mid-campaign. The setup is already done: domains, SPF, DKIM, DMARC and forwarding are configured before you log in.
Watch out for: Prewarmed inboxes sit on domains the vendor supplies, not your brand, and cost more than double a fresh inbox. Every result on the site comes from the vendor's own customer stories. It is infrastructure only, so you still need a sequencer such as Instantly or Smartlead.
Overview
Warm Inboxes, run by Upscale B2B, sells the mailboxes cold email is sent from. Its prewarmed inboxes are official Google Workspace, Microsoft 365 or Azure accounts on free prewarmed .com domains, sold in packs of three or as Azure tenants of 100, and ready to send on arrival with no warmup wait.
Once a campaign works, fresh inboxes on your own branded domains add sending capacity at a lower cost per inbox after a 14 to 21 day warmup. Domains, SPF, DKIM, DMARC and forwarding are configured for you, sending runs across US and EU IPs, and support is by WhatsApp around the clock. The vendor lists Instantly, Smartlead, EmailBison and ManyReach among the senders it works with.
Prewarmed Google or Microsoft inboxes cost $8 each a month ($6 on quarterly billing), and an Azure tenant of 100 inboxes is $69 a month. Fresh Google Workspace inboxes start at $3.50 and Microsoft 365 at $3 an inbox a month, with lower prices on yearly billing and at volume.
Who it's for
Best for
- Agency recruiters launching cold business development email fast
- Teams whose sending domains got burned mid-campaign
- Desks scaling outreach across many inboxes
- Instantly and Smartlead users who want inboxes set up for them
Not ideal for
- Recruiters who only send from their main company mailbox
- Teams that want inboxes on their own brand from day one at the lowest price
- Buyers looking for a sequencer or lead database
Key features
Prewarmed inboxes. Official Google Workspace, Microsoft 365 and Azure inboxes on free prewarmed .com domains, ready to send the day you buy them, with replacements dropped in the same day when a domain burns.
Fresh inboxes at volume. Inboxes on your own branded domains for scaling a campaign that works, with SPF, DKIM, DMARC and forwarding set up before you log in.
Works with your sender. Built to plug into Instantly, Smartlead, EmailBison and ManyReach, with US and EU IP infrastructure and 24/7 WhatsApp support.
Pricing
| Plan | Price | What you get |
|---|---|---|
| Prewarmed Google or Microsoft | $8/inbox/mo | Packs of 3 with a free domain; $6 on quarterly billing |
| Prewarmed Azure tenant | $69/mo | 100 inboxes per tenant ($0.69 each) |
| Fresh Google Workspace | $3.50/inbox/mo | Your domains, 14 to 21 day warmup; less yearly and at volume |
| Fresh Microsoft 365 | $3/inbox/mo | Your domains; $2 an inbox billed yearly |
Prices are per inbox per month. Prewarmed Google or Microsoft inboxes come in packs of 3 with a free prewarmed .com domain at $8 an inbox monthly, $7 on 2-month or $6 on quarterly billing; a prewarmed Azure tenant of 100 inboxes is $69 a month. Fresh inboxes on your own domains need a 14 to 21 day warmup: Google Workspace from $3.50 an inbox monthly (down to $2 yearly at 100+ inboxes) and Microsoft 365 from $3 monthly ($2 yearly). Creating an account needs no card. Confirm current terms on the vendor site.
Checked 19 Oct 2026. Vendors change prices without notice.
Is Warm Inboxes expensive?
Warm Inboxes starts at $3/inbox/mo. We list 35 deliverability tools in total. 4 have a free tier, and those with a public price typically start around $15 a month.
- 1 quote-based
- 4 free tier
- 34 public price
Worked out automatically from every deliverability listing, so it updates as the directory changes.
Pros and cons
Pros
- Prewarmed inboxes send on day one
- DNS and authentication set up for you
- Same-day replacement inboxes when a domain burns
Cons
- Prewarmed inboxes use vendor-supplied domains
- Results quoted are the vendor's own
- Needs a separate sending tool
Integrations
Instantly Smartlead EmailBison ManyReach HubSpot Apollo Cloudflare GoDaddy
What's new at Warm Inboxes
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How Warm Inboxes compares
See all Warm Inboxes alternatives, with what each one does differently and a head to head for every pairing.
| Tool | Free tier | From | MCP | API | Compare |
|---|---|---|---|---|---|
| Warm Inboxes (this tool) | – | $3/inbox/mo | – | – | |
 Premium Inboxes Client-owned Google and Microsoft inboxes on your own domains from $3.50 an inbox, set up and loaded into your sender for you. | – | $3.50/inbox/mo | – | – | Compare |
| | – | $3/mailbox/mo | – | – | Compare |
 InboxKit Mailboxes from $2.50 each a month, a lower price if you can wait out warmup on fresh inboxes. | – | $2.50/mailbox/mo | – | ✓ | Compare |
Premium Inboxes$3.50/inbox/mo
Client-owned Google and Microsoft inboxes on your own domains from $3.50 an inbox, set up and loaded into your sender for you.
$3/mailbox/mo
Self-serve mailboxes from $3 each a month, if you want to manage domains and setup yourself.
InboxKit$2.50/mailbox/mo API
Mailboxes from $2.50 each a month, a lower price if you can wait out warmup on fresh inboxes.
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