Cold email remains the highest-ROI outbound channel in B2B — agencies report $36 returned for every $1 spent. But there's a brutal catch: Google's February 2024 spam crackdown means any domain without proper warmup gets nuked. A sales team at a 50-person startup bought 10 new domains for outbound, started sending immediately, and watched all 10 land in spam within 48 hours. That's $500 in domains and 2 weeks of pipeline generation — gone.
Warmbox proved the market is real, hitting $1M+ ARR within its first year. Instantly.ai bundles warmup into their cold email platform. Lemwarm (by Lemlist) charges $29/mo per inbox. The demand is insatiable because it's not optional — without warmup, cold email simply doesn't work anymore.
The gap? Current tools are either bundled into expensive platforms (Instantly at $30/mo minimum, Lemlist at $59/mo) or standalone but limited. A focused warmup tool at $29/mo with better analytics (deliverability score, inbox placement rate, spam trigger analysis) and support for Google Workspace + Outlook + custom SMTP could capture the standalone market that Warmbox pioneered.
💰 Revenue Blueprint
Three-tier value ladder to monetize from day one
Free email deliverability audit — check if your domain is blacklisted, SPF/DKIM configured, spam score
1 inbox warmup, gradual ramp-up, engagement simulation, deliverability dashboard, Google + Outlook support
5 inboxes, team dashboard, priority warmup speed, custom warmup schedules, API access, Slack alerts on issues
Why Now?
Google's Feb 2024 spam update made warmup mandatory. Microsoft following suit. Cold email volume keeps growing (estimated 350B emails/day by 2025). Every new domain needs warmup.
📊 Market Evidence
The Market Gap
Warmbox ($15-69/mo) is standalone but basic analytics. Instantly bundles warmup but forces you into their full platform. No tool focuses on warmup + deliverability intelligence as the core product.
Revenue Examples
Estimated from team size and pricing
Raised $0, bootstrapped to millions
🏆 Competitor Landscape
How existing players stack up in this market
| Competitor | Pricing | Notes |
|---|---|---|
| Warmbox | $15-69/mo | Pioneer in standalone warmup |
| Instantly.ai | $30/mo | Bundles warmup into cold email platform |
| Lemwarm | $29/mo | By Lemlist, tied to their ecosystem |
Pioneer in standalone warmup
Bundles warmup into cold email platform
By Lemlist, tied to their ecosystem
Launch Strategy
1) Build warmup network with 500+ seed mailboxes. 2) Free deliverability checker as lead magnet — viral potential. 3) Target cold email communities: r/coldemail, Cold Email Twitter, agency Slack groups. 4) Partner with cold email course creators for affiliate. 5) Content play: 'Is your domain about to get blacklisted?' diagnostic tool.
🛠️ Recommended Tech Stack
Suggested tools and technologies to build this idea
Why this stack: Email warmup requires persistent SMTP connections and scheduled sending. Self-hosted infra on Hetzner keeps costs low. Redis queues manage warmup schedules.
Strengths
- ✓Non-optional tool — cold email doesn't work without it
- ✓High willingness to pay ($29-49/mo is cheap vs lost deals)
- ✓Recurring and sticky
- ✓Free deliverability check is a strong viral lead magnet
Risks
- ⚠Google could change warmup detection
- ⚠Instantly bundling warmup free reduces standalone appeal
- ⚠Need to maintain large mailbox network
Score Breakdown
High demand, proven revenue, low competition — a strong opportunity
Market (20%) + Revenue (20%) + Trend (15%) + Competition (15%) + Build (15%) + Pricing (15%)
Warmbox, Instantly prove massive demand
Multiple tools doing $100K+ MRR
Google spam crackdown makes this more essential every month
Several players but room for differentiation
Moderate — need mailbox network infrastructure
Strong willingness to pay, non-optional tool
🚀 Start Building
Copy a prompt into your favorite AI coding tool and start building this idea right now.
Build a SaaS product called "Email Warmup Tool". ## Product Overview Warm up cold email domains automatically to keep deliverability high. $29-49/mo. ## Problem Cold email is the #1 outbound channel for B2B SaaS, agencies, and recruiters. But Google and Microsoft keep tightening spam filters. A new domain sending 50 cold emails on day one goes straight to spam. You need weeks of 'warmup' — gradually increasing send volume with real engagement signals. ## Solution An automated warmup service that sends realistic emails between a network of real mailboxes, opens them, replies to them, and marks them as important — training email providers that your domain is legitimate. ## Target Audience B2B sales teams, SDRs, cold email agencies, recruiters, SaaS founders doing outbound ## Tech Stack - Next.js 15 (App Router) with TypeScript - Tailwind CSS v4 for styling - Supabase for auth, database, and storage - Vercel for deployment - shadcn/ui for UI components - Framer Motion for animations ## MVP Features to Build 1. Landing page with clear value proposition 2. User authentication (sign up, sign in, forgot password) 3. Core product functionality based on the solution above 4. Dashboard for users to manage their data 5. Pricing page with at least 2 tiers (free + paid) 6. Basic settings/profile page ## Known Competitors Warmbox, Instantly.ai, Lemwarm ## Key Risks to Address Google could change warmup detection Instantly bundling warmup free reduces standalone appeal Need to maintain large mailbox network ## Deployment 1. Set up Supabase project and configure environment variables 2. Deploy to Vercel with `npx vercel --prod` 3. Set up custom domain 4. Configure Supabase RLS policies for security ## Instructions Start by creating the project structure, then build the landing page first. Use server components where possible. Make it mobile-responsive from the start. Focus on getting the core value loop working before adding polish.