About
Cold email infrastructure, run by people who send cold email
WarmInboxes sells prewarmed and fresh Google Workspace, Microsoft 365 and Azure mailboxes for cold email, with the domain, the DNS and the warmup done before handover. It exists because the agency that built it needed infrastructure that held under a million sends a month and could not buy it. Everything on this site, the product, the free tools and the published studies, comes out of running that agency.
What we do
Two products. Prewarmed inboxes come on a free prewarmed .COM or .CO domain that has already been warmed, so they send the day they land. Fresh inboxes are built on domains you own, warmed by our technicians for 14 to 21 days, and cost about a third as much at volume. Every order is delivered within 48 to 72 hours of payment with SPF, DKIM, DMARC and forwarding configured and verified by hand, on Google Workspace, Microsoft 365 or isolated Azure tenants. The whole sequence is on how it works and every price is published as plain text at /price.md.
Around the product: 55 free deliverability tools that run without an account, also callable as an API and an MCP server; a free database of 999 B2B lead lists; 102 guides; and three published studies drawn from our own sending, with the data downloadable. 500+ teams run their cold email infrastructure on WarmInboxes.
How the tools and studies are written
Every free tool states what it cannot see rather than filling the gap. There are no invented reputation scores, because receivers hold that data privately; optional records are marked optional rather than shown as failures; a check that cannot be run is named as not run rather than folded into a pass. The studies follow the same rule: every figure is computed from a data file, the fieldwork window and the sample size are on the page, no client or vendor is named, and the months that went badly are published with the ones that went well. The studies and the changelog, which lists corrections alongside additions, are where that shows most.
Certified by the platforms we build on
Where it came from
- August 2025app.upscaleb2b.com, the first portalOur first customer portal, app.upscaleb2b.com. It took orders. No API, no automation.
- October 2025app.warminboxes.com, with an API, an MCP server and a CLIThe portal moved to app.warminboxes.com. It now has a REST API, an MCP server, and the wib CLI, all using the same API key.
The full record, including what was fixed and when, is the changelog.
Who
Huzayfa Majeed founded WarmInboxes and runs the cold email agency it was built for, which sends more than a million cold emails a month on the same infrastructure WarmInboxes sells. He is an Instantly Certified Expert, a Smartlead Partner, Clay Verified and a PlusVibe Technology Partner, and he built the free deliverability tools on this site so the checks his team runs before every campaign are public. His page is Huzayfa Majeed.
The company is Upscale Systems LLC, in Pembroke Pines, FL. The agency side runs as Upscale B2B, which is where the sending volume behind the studies comes from.
Contact
Support is on WhatsApp at +1 904 736 2539, 24/7, and by email at [email protected]. Developers and AI agents start at /developers; the machine-readable index of the site is /llms.txt.