The SPACLE Framework - Module 4
Set up your cold email infrastructure properly. Master domains, authentication, warmup, and deliverability optimization.
The technical foundation that ensures your emails actually reach inboxes. Without proper setup, even perfect emails land in spam. This module covers the infrastructure every startup needs.
You spent hours crafting the perfect cold email. Researched your prospects. Personalized every line. Hit send with confidence. Then... crickets. Zero opens. Zero replies.
The brutal truth? Your emails never reached the inbox. They landed in spam because you skipped the technical foundation that Gmail and Outlook demand. 90% of cold email failures aren't caused by bad copy—they're caused by bad infrastructure.
Most founders think: "I'll just buy a list and start sending." Wrong. Without proper domain setup, DNS authentication (SPF, DKIM, DMARC), dedicated sending domains, email warmup, and the right platform—you're burning leads before they ever see your message.
This module is your deliverability insurance policy. You'll learn why you must never use your main domain for cold email, how to set up sending domains correctly, whether to choose DIY infrastructure or SMTP providers, which platforms actually deliver, and the warmup protocols that protect your sender reputation.
Skip this module, and your campaign fails before it starts. Master it, and you'll have 85%+ inbox placement. Let's build it right. 🛠️
90% of startup cold email failures are due to deliverability issues, not bad copywriting. If your emails land in spam, nobody sees your brilliant messaging. Technical setup is NOT optional—it's foundational.
You've crafted the perfect cold email. You've researched your prospects. You've personalized every message. You hit send...and nothing happens. Zero replies. Zero opens. Your emails disappeared into the void.
The problem isn't your messaging—it's that your emails never reached the inbox. They landed in spam, were blocked by email providers, or triggered security filters before anyone could read them.
This is the harsh reality: technical deliverability infrastructure determines whether your cold email campaign succeeds or fails. No amount of brilliant copywriting can overcome emails that land in spam folders.
of cold email failures are due to technical deliverability issues, not bad copywriting or targeting
minimum warmup period required before scaling to full sending volume
emails per day per inbox maximum to maintain deliverability (start at 10-20/day)
total monthly cost per sending domain (domain + inbox + warmup tool)
This module covers the complete technical infrastructure you need to send cold emails that actually reach inboxes. By the end, you'll understand:
Why you must NEVER use your main company domain for cold email, how to set up dedicated sending domains, and how to protect your brand reputation
Choose between DIY setup (Google Workspace/Microsoft 365) or SMTP providers, then configure DNS records (SPF, DKIM, DMARC) to authenticate your emails
Understanding what warmup really means, how email providers evaluate sender reputation, the mechanics of warmup networks, and why it never actually stops
Track critical metrics (inbox placement rate, bounce rate, spam complaints) to catch deliverability issues before they kill your campaigns
Comprehensive comparison of the top 8 cold email platforms—all can send emails, but differ in prospecting features, pricing, and capabilities
Rule #1: NEVER use your main company domain for cold email. If you ruin its reputation, all your emails (transactional, customer support, team communication) will go to spam. Your primary domain is sacred—it's for customers, investors, partners, and internal communication only.
Send cold email from:
[email protected]
Risk: One spam complaint or deliverability issue ruins your primary domain forever. All your customer emails, password resets, invoices, team communication—everything goes to spam.
Buy 2-3 similar sending domains:
[email protected]
[email protected]
Benefit: Protect your main domain while scaling outreach safely. If one sending domain gets flagged, your primary domain stays pristine.
Let's walk through a complete example using a fictitious startup called FlowMetrics, a SaaS analytics platform.
flowmetrics.com
Used for: Customer support, product emails, invoices, password resets, team communication, investor updates
Example inboxes:
Domain 1: tryflowmetrics.com
Naming convention: "Try" + brand name (common pattern)
Inboxes created (4 per domain):
💡 Pro tip: Use real first names of your team members. Makes it authentic and easier to manage replies.
Domain 2: getflowmetrics.com
Naming convention: "Get" + brand name (action-oriented)
Inboxes created (4 per domain):
💡 Pro tip: Keep the same first names across domains for consistency. Sarah manages replies from both sarah@try... and sarah@get...
Domain 3: helloflowmetrics.com
Naming convention: "Hello" + brand name (friendly approach)
Inboxes created (4 per domain):
💡 Pro tip: With 3 domains × 4 inboxes = 12 total inboxes. Sarah now has 3 inboxes (one per domain), giving her 90 emails/day capacity (3 × 30).
If your main domain is yourbrand.com, here are proven naming patterns:
Cost: $10-15/domain/year. Where to buy: Namecheap, Google Domains, Cloudflare.
Before we dive into the math, let's clarify the basic building blocks of cold email infrastructure:
Domain: This is your email address's ending—the part after the "@" symbol. For example, in [email protected], the domain is trystartup.com. You'll buy multiple domains similar to your main brand (like trystartup.com, getstartup.com) specifically for cold email to protect your main company domain.
Inbox (Email Account): This is a complete email address like [email protected]. Each domain can host multiple inboxes—typically 3-5 different email accounts. For example, on trystartup.com you could have [email protected], [email protected], [email protected], etc. Each inbox can send emails independently.
Sending Volume: This is the total number of emails sent per day or month. For example, if you send 360 emails/day, that's your daily sending volume. This includes BOTH your initial emails to new prospects AND all automated follow-up emails in your sequences. It's your complete outbound output.
Now, understanding the domain → inbox → volume relationship is critical for planning. Here's the math that determines your infrastructure capacity:
⚠️ Critical: This sending volume includes BOTH initial emails to new contacts AND automated follow-ups. Your actual new prospect reach will be smaller than total volume.
Domains: 3 sending domains
Inboxes: 12 total (4 per domain)
Daily capacity: 360 emails/day (12 × 30)
Monthly volume: 7,200 emails (360 × 20 days)
💡 Real-world capacity: With a 4-email sequence (1 initial + 3 follow-ups), you can reach 1,800 new prospects/month (7,200 ÷ 4 = 1,800). That's 90 initial emails/day + 270 follow-ups/day = 360 total.
💰 Monthly cost: Domains ($3) + Google Workspace ($72) = $75/mo
✅ Best for: Testing campaigns, founder-led outreach, early-stage startups
Domains: 8 sending domains
Inboxes: 32 total (4 per domain)
Daily capacity: 960 emails/day (32 × 30)
Monthly volume: 19,200 emails (960 × 20 days)
💡 Real-world capacity: With a 4-email sequence, you can reach 4,800 new prospects/month (19,200 ÷ 4 = 4,800). That's 240 initial emails/day + 720 follow-ups/day = 960 total.
💰 Monthly cost: Domains ($8) + Google Workspace ($192) = $200/mo
✅ Best for: Building momentum, consistent pipeline, 1-2 sales reps
Domains: 20 sending domains
Inboxes: 80 total (4 per domain)
Daily capacity: 2,400 emails/day (80 × 30)
Monthly volume: 48,000 emails (2,400 × 20 days)
💡 Real-world capacity: With a 4-email sequence, you can reach 12,000 new prospects/month (48,000 ÷ 4 = 12,000). That's 600 initial emails/day + 1,800 follow-ups/day = 2,400 total.
💰 Monthly cost: Domains ($20) + Google Workspace ($480) = $500/mo
✅ Best for: Growing sales teams, multiple campaigns, A/B testing at scale
Domains: 50 sending domains
Inboxes: 200 total (4 per domain)
Daily capacity: 6,000 emails/day (200 × 30)
Monthly volume: 120,000 emails (6,000 × 20 days)
💡 Real-world capacity: With a 4-email sequence, you can reach 30,000 new prospects/month (120,000 ÷ 4 = 30,000). That's 1,500 initial emails/day + 4,500 follow-ups/day = 6,000 total.
💰 Monthly cost: Domains ($50) + Google Workspace ($1,200) = $1,250/mo
✅ Best for: Agencies, enterprise sales teams, multi-product/region outbound
Why does 7,200 emails/month only reach 200-250 new prospects? Because your total volume is split between initial outreach and follow-ups:
💡 Planning tip: To calculate how many NEW prospects you'll reach monthly: (Total monthly volume ÷ number of emails in your sequence) = new prospects reached
Use this step-by-step formula to plan your setup:
⚠️ Pro tip: Always round UP and add 1-2 extra domains as buffer. If calculation shows 5 domains, get 6-7. This gives you room for domain rotation, A/B testing, and handling any deliverability issues without stopping campaigns.
Once you have your sending domains set up, you need two critical components: (1) professional email hosting to actually send emails, and (2) authentication records to prove your emails are legitimate. Let's cover both.
You need professional email hosting for your sending domains. The two main options are Google Workspace and Microsoft 365 (Outlook). Both work well, but they have different strengths.
Pricing: $6/user/month (Business Starter)
Deliverability: Excellent for cold email
Setup: Very straightforward
Warmup friendly: Yes
✅ Pros:
❌ Cons:
Pricing: $6/user/month (Business Basic)
Deliverability: Very good for cold email
Setup: Slightly more complex
Warmup friendly: Yes
✅ Pros:
❌ Cons:
Use Google Workspace for your first 2-3 sending domains. It has the best deliverability, easiest setup, and works flawlessly with all cold email tools (Instantly, Smartlead, Lemlist). Once you're sending 500+ emails/day and need to scale, you can add Microsoft 365 domains for diversification.
After choosing your email host, you need to configure authentication records in your DNS settings. Email providers (Gmail, Outlook) check these records to verify you're legitimate. Without proper authentication, you're marked as suspicious immediately.
There are four critical DNS records you need to configure:
What it does: Lists which mail servers are authorized to send email from your domain.
Why it matters: Prevents spammers from impersonating your domain.
Setup: Add as TXT record in your domain DNS settings.
What it does: Adds a digital signature to your emails proving they haven't been tampered with.
Why it matters: Verifies email integrity and authenticity.
Setup: Your cold email tool (Instantly, Smartlead) will generate DKIM records for you. Add them as TXT records to DNS.
What it does: Tells email providers what to do if SPF/DKIM checks fail.
Why it matters: Provides additional layer of authentication and reporting.
Startup recommendation: Start with "p=none" (monitoring mode), move to "p=quarantine" after 30 days.
What it does: Uses your domain for email tracking links (not tool's domain).
Why it matters: Prevents "unknown link" spam triggers from generic tracking domains.
Example: Instead of track.instantly.com, use track.tryyourcompany.com
After adding DNS records, you must verify they're working correctly. Here's how:
What if you could skip all the technical complexity? SMTP providers offer a done-for-you infrastructure solution where domains, email hosting, DNS records, authentication, and deliverability are managed automatically. You focus on sending emails—they handle everything else. Note: SMTP providers use different pricing models—Inframail charges a flat rate ($99/mo for unlimited inboxes), while Maildoso (~$3/inbox) and Mailreach (~$18/inbox) charge per-inbox. Most SMTP options are cheaper than DIY Google Workspace at scale.
SMTP (Simple Mail Transfer Protocol) providers are specialized email infrastructure services built specifically for cold email at scale. Instead of buying domains, setting up Google Workspace, configuring DNS records, and managing everything yourself, SMTP providers give you pre-configured, ready-to-use email infrastructure in minutes.
Think of it as "email infrastructure as a service"—you rent inboxes that come with domains, DNS records, and technical setup already handled. Note: Most SMTP providers still require warmup (2-3 weeks)—the key benefit is they handle all the technical complexity, not that you skip warmup entirely.
You handle: Nothing. They provide domains.
They handle: Buy, register, and manage sending domains automatically. You never touch domain registrars.
You handle: Nothing. Infrastructure included.
They handle: Full email server infrastructure. No Google Workspace or Microsoft 365 needed.
You handle: Nothing. Pre-configured.
They handle: All authentication records configured perfectly. No DNS headaches.
You handle: Nothing. Built-in.
They handle: Custom tracking domains set up and configured for optimal deliverability.
You handle: Enable warmup in dashboard.
They handle: Automated warmup process included in platform. Still takes 2-3 weeks, but managed automatically. Some premium providers offer pre-warmed inboxes for immediate sending.
You handle: Nothing. Automated.
They handle: 24/7 monitoring, automatic replacements if inbox health degrades.
Pricing: $100/month for 32 inboxes
Per inbox: ~$3.13/inbox/month
Setup time: 24-48 hours
✅ Pros:
Best for: Budget-conscious founders who want full automation at the lowest cost
Pricing: $99/mo (1 IP) or $249/mo (3 IPs)
Inboxes included: UNLIMITED inboxes (flat rate)
Setup time: 24-48 hours
✅ Pros:
❌ Cons:
Best for: Startups scaling to 32-100 inboxes ($99 tier) or 100-300 inboxes ($249 tier). Not ideal for enterprise scale on basic tier.
Pricing: $576/month for 32 inboxes
Per inbox: $18/inbox/month
Setup time: Instant activation
✅ Pros:
Best for: High-volume senders prioritizing maximum deliverability and premium support
Many cold email platforms (Instantly, Smartlead, etc.) also offer their own SMTP services:
These are convenient if you're already using their platform, but standalone providers (Maildoso, Inframail, Mailreach) give you more flexibility.
Example: 32 inboxes across 10 domains
Total: $202/month
✅ Pros:
❌ Cons:
Best for: Technical founders comfortable with DNS setup who want premium deliverability and full control
Example: 32 inboxes fully managed
Total: $99-576/month
✅ Pros:
❌ Cons:
Best for: Non-technical founders who want automation, or anyone who values time saved over full control
Choose DIY ($202/month): If you're technical, want best-in-class deliverability (Gmail/Outlook reputation), plan to use inboxes for team communication beyond cold email, or want full control over your infrastructure. Requires DNS setup but gives you premium infrastructure.
Choose SMTP Providers ($99-576/month): If you're non-technical, want zero setup hassle, need automated monitoring, or value time saved over control. Inframail ($99/mo unlimited) is cheapest overall. Maildoso ($110/mo for 32) is best budget per-inbox option. Premium options ($576/mo) offer white-glove service.
| Option | Setup Required | Monthly Cost | Best For |
|---|---|---|---|
| 🏆 SMTP: Inframail | Zero | $99/mo (unlimited inboxes) | Best value + scaling beyond 32 inboxes |
| SMTP: Maildoso | Zero | $110/mo (32 inboxes) | Budget per-inbox option |
| DIY: Google Workspace | Manual DNS | $202/mo (32 inboxes) | Technical + want premium deliverability |
| SMTP: Mailreach | Zero | $576/mo (32 inboxes) | Premium automation + white-glove |
* Comparison for 32 inboxes. Inframail uses flat-rate unlimited pricing ($99 or $249/mo for unlimited inboxes), becoming more cost-effective at scale. Other SMTP providers charge per-inbox. DIY requires separate domain purchase ($10/mo) and manual DNS configuration.
⚠️ Inframail IP Limitation: The $99 tier (1 dedicated IP) is safe for approximately 50-100 inboxes. Beyond 100 inboxes, you risk damaging sender reputation by overloading a single IP. If scaling beyond 100 inboxes, upgrade to the $249 tier (3 IPs) to distribute sending load and maintain deliverability.
Brand new domains have ZERO reputation. Email providers don't trust you yet. Warmup gradually builds trust by simulating normal email activity before launching cold campaigns.
Imagine you just registered a brand new phone number and immediately started making 200 cold calls per day. Phone carriers would flag you as a spam caller within hours. Email works exactly the same way.
When you register a new domain and set up email hosting, email providers like Gmail and Outlook have never seen your domain send emails before. They have zero data on whether you're a legitimate business or a spammer. You have no "sender reputation"—the trust score that email providers assign to every domain and IP address.
If you immediately start blasting 100+ cold emails per day from a brand new domain, here's what happens:
Email warmup solves this by gradually introducing your domain to email providers as a legitimate sender. Instead of sudden high-volume sending that screams "spammer," you slowly ramp up email activity over 2-3 weeks, demonstrating consistent, normal email behavior that builds trust.
Warmup tools (built into most cold email platforms or standalone services like Instantly Warmup, Smartlead Warmup, or Mailwarm) automate this process by:
Your inbox joins a network of thousands of other inboxes also warming up. Your domain automatically sends 10-50 emails per day to these accounts (increasing gradually over weeks).
Those accounts reply to your emails. This creates two-way conversation, showing email providers that real people engage with your emails (the strongest trust signal).
Warmup accounts open your emails, click links inside them, and mark them as "not spam" if they land in spam folders. This teaches Gmail/Outlook's algorithms that your emails are wanted.
Week 1: 10-20 emails/day → Week 2: 20-30/day → Week 3: 30-40/day. This gradual ramp-up mimics how real businesses naturally increase their email activity, avoiding sudden volume spikes that trigger spam filters.
Gmail, Outlook, and other providers use sophisticated algorithms to evaluate sender reputation. Here's what they monitor:
Many founders think warmup is a one-time 2-3 week process, then they turn it off. This is wrong. Email warmup should run continuously in the background forever, even after you start sending cold emails. Here's why: sender reputation is not static—it's constantly being recalculated based on recent activity. If you stop generating positive signals (opens, replies, engagement), your reputation slowly degrades. Keep warmup running at 30-50 emails/day permanently alongside your cold email campaigns. This ensures a steady stream of positive engagement signals that maintain your sender reputation over time.
| Week | Warmup Emails/Day | Cold Emails/Day | Action |
|---|---|---|---|
| Week 1 | 10-20 | 0 | Start warmup only |
| Week 2 | 20-30 | 0 | Continue warmup |
| Week 3 | 30-40 | 10-20 | Start cold email (TEST) |
| Week 4 | 40 | 30-40 | Increase volume |
| Week 5+ | 40-50 | 50-100 | Full scale (ongoing warmup) |
You can't improve what you don't measure. Monitor these metrics daily to catch deliverability issues before they kill your campaigns:
Target: Under 3%
Warning: 3-5%
Critical: Above 5%
What it means: Percentage of emails that can't be delivered (invalid addresses, full inboxes).
Fix: Use email verification (ZeroBounce, NeverBounce) before sending. Remove bounced addresses immediately.
Target: Under 0.1%
Warning: 0.1-0.3%
Critical: Above 0.3%
What it means: People manually marking your email as spam.
Fix: Improve targeting (wrong ICP), better copy (too salesy), clear unsubscribe link, reduce volume.
Target: 40-60%
Warning: 25-40%
Critical: Below 25%
What it means: If opens suddenly drop, you might be landing in spam.
Fix: Check spam folder placement with seed testing. Review DNS records. Slow down sending.
Target: 1-3%
Warning: 0.5-1%
Critical: Below 0.5%
What it means: Engagement rate. Gmail/Outlook reward inboxes with high reply rates.
Fix: Better targeting, more personalization, stronger value proposition, clearer CTA.
All of these tools can send cold emails, but they differ in how they help you find and manage prospects. Some include built-in prospecting and databases, while others focus purely on sending campaigns. Choose based on your workflow and whether you need help finding prospects or already have your lead sources.
Best for: Best value for startups on a budget
Most popular choice for startups. Unlimited email accounts, built-in lead database with 160M+ contacts, email verification, unlimited warmup, inbox rotation, A/B testing, and unified inbox. Simple interface with excellent deliverability. Best bang for your buck.
💰 Pricing: $30/mo (1,000 leads) • 📧 Sending: Full email sending platform + lead database
Best for: Advanced deliverability features
Premium cold email platform with unlimited mailboxes, advanced AI warmup, SmartDelivery (inbox placement testing), unified master inbox, white-label options, and sophisticated analytics. More advanced than Instantly with enterprise-grade deliverability optimization. Strong integrations with prospecting tools.
💰 Pricing: $39/mo (2,000 leads) • 📧 Sending: Full email sending platform
Best for: Budget-conscious startups
Most affordable dedicated sending platform at $27/mo. Unlimited email accounts, built-in warmup, sequence builder, unified inbox, email verification, and solid deliverability. Great for bootstrapped startups prioritizing cost efficiency without sacrificing essential features.
💰 Pricing: $27/mo (2,000 prospects) • 📧 Sending: Full email sending platform
Best for: AI-powered prospecting + sending in one
100M+ verified B2B contacts with AI scoring (1-100) based on ICP fit. AI analyzes prospects' online presence and crafts hyper-personalized emails referencing recent activity. Includes built-in email sending, warmup, and deliverability management. Complete end-to-end solution from prospecting to campaign delivery.
💰 Pricing: $49-299/mo • 📧 Sending: Full prospecting + sending platform
Best for: LinkedIn signal prospecting + sending
Chrome extension + cold email sender. Export LinkedIn engagement (post likes, comments, profile views), enrich with verified emails, generate ChatGPT icebreakers, and send campaigns directly from the platform. Includes email warmup, sequence builder, and analytics. Perfect for LinkedIn-first prospecting.
💰 Pricing: $39/mo • 📧 Sending: Built-in cold email sending platform
Best for: Massive B2B database + sending
250M+ contact database with AI-powered buyer intent signals (job changes, funding, hiring). Advanced search filters, email verification, and built-in email sequences with sending infrastructure. AI writes personalized sequences. Multi-channel outreach (email + LinkedIn). Best for teams wanting database + sending in one platform.
💰 Pricing: $49-149/mo • 📧 Sending: Full database + sending platform
Best for: Creative personalization + UX
Best-in-class user experience with advanced personalization. Image/video personalization, Lemwarm (warmup tool), LinkedIn automation, custom landing pages, and beautiful interface. Higher price point but worth it for teams prioritizing ease of use and creative outreach campaigns.
💰 Pricing: $59/mo (Starter) • 📧 Sending: Full email sending platform
Best for: AI-powered personalization at scale
Advanced cold email platform with AI-powered personalization, unlimited email accounts, automated warmup, inbox rotation, and powerful sequence builder. Focus on AI-driven content generation and dynamic personalization. Strong deliverability features with detailed analytics and A/B testing.
💰 Pricing: $99/mo • 📧 Sending: Full email sending platform with AI personalization
Need help finding prospects? Choose tools with built-in databases and prospecting:
Already have your prospects? Choose dedicated sending platforms:
Master cold email copywriting: subject lines, personalization, value propositions, and CTAs that get responses.
Continue to Module 5 →