Cold Emailing
Feb 4, 2026
CEO and co-founder
Cold Email Infrastructure Guide: How to Scale Deliverability and Protect Margins
What is cold email infrastructure?
Cold email infrastructure is the backend plumbing that delivers your message to the inbox. It includes four core components: domains, DNS authentication records, IP addresses, and mailboxes. Each piece plays a specific role in proving your identity and establishing your reputation with inbox providers.
I think of infrastructure like a delivery fleet. You can rent expensive taxis (Google Workspace at $7-8.40 per seat), ride a crowded bus where one bad passenger gets everyone kicked off (shared IP pools), or operate your own fleet where your driving record alone determines your insurance rates (dedicated infrastructure).
Your infrastructure stack handles two critical jobs:
Identity verification: DNS records (SPF, DKIM, DMARC) prove you are who you claim to be
Reputation management: IP addresses and domain health scores determine whether inbox providers trust you
When ISPs check recipients' engagement and see low open rates or frequent spam complaints, they treat those emails as spammy. Your infrastructure's job is to pass authentication checks and maintain the reputation scores that keep you out of spam folders.
For a complete walkthrough of the technical setup process, our Ultimate Cold Email Infrastructure Guide for 2025 covers everything from domain selection to inbox provisioning.
The economic impact of infrastructure choices on agency margins
Infrastructure costs create one of two outcomes for agencies: predictable margins that scale with client growth, or a squeeze that gets worse with every new account you sign.
The Google Workspace trap
Google Workspace Business Starter costs $7-8.40 per user per month depending on billing frequency. The math gets ugly fast:
Inbox Count | Google Workspace Monthly Cost | Annual Cost |
|---|---|---|
50 inboxes | $350-420 | $4,200-5,040 |
100 inboxes | $700-840 | $8,400-10,080 |
200 inboxes | $1,400-1,680 | $16,800-20,160 |
That is just the platform fee. You still need domains and warmup tools.
Traditional TLDs like .com and .net average roughly $12/year according to Namecheap's domain pricing analysis, which works out to $1/month per domain. For 50 inboxes across 25 domains (2 inboxes per domain), add another $68.50/month.
Email warmup tools like Warmbox cost $15 per mailbox per month for 50 emails per day. For 50 inboxes, that adds $750/month to your stack.
Total monthly cost for 50 inboxes on Google Workspace:
Platform: $350-420
Domains: $25
Warmup: $750
Total: $1,168.50 - $1,238.50/month
The margin threshold: Infrastructure should consume less than 25% of your client billings. At $1,125/month for 50 inboxes serving 10 clients at $3,000/month average retainer, you're spending 37% of one client's revenue just on infrastructure. That's 12 percentage points above the sustainable ceiling that kills margins.
The flat-rate alternative
Inframail's Unlimited Plan costs $129/month for unlimited inboxes with 1 dedicated US-based IP. The Agency Pack runs $327/month with 3 dedicated IPs.
Inbox Count | Inframail Monthly Cost | Annual Cost |
|---|---|---|
50 inboxes | $129 | $1,548 |
100 inboxes | $129 | $1,548 |
200 inboxes | $129 | $1,548 |
Total monthly cost for 50 inboxes on Inframail:
Platform: $129
Domains: $25
Warmup: External tool required (but savings cover it)
Total: $197.50/month before warmup
The platform savings alone ($350-420 minus $129 = $221-291/month) more than cover external warmup costs for a reasonable inbox count.
"Inframail makes it remarkably easy to purchase domains, configure them correctly, create inboxes, and initiate warm-up immediately. The level of automation is exceptional and clearly designed for serious operators." - Verified user review of Inframail
For a detailed breakdown of how these costs compare across providers, check out our cold email infrastructure ROI calculator.
Key components of high-deliverability infrastructure
Deliverability depends on three technical pillars: authentication protocols, domain strategy, and inbox configuration. Get any of these wrong and your campaigns hit spam regardless of how good your copy is.
Authentication protocols: Your digital ID cards
Every email you send goes through verification checks. Three protocols determine whether inbox providers trust your identity:
1. SPF (Sender Policy Framework):
This record lists every server authorized to send email from your domain. SPF helps prevent outgoing email from being marked as spam by telling receiving servers which IP addresses are legitimate senders for your domain.
2. DKIM (DomainKeys Identified Mail):
This adds a digital signature to every email. The receiving server checks your public key (published in DNS) against the private key used to sign the message. DKIM verification confirms the signature is valid, and DKIM alignment (required for DMARC) checks whether the signing domain matches the From header domain.
3. DMARC (Domain-based Message Authentication, Reporting and Conformance):
This policy tells receiving servers what to do when messages fail SPF or DKIM checks. Options include reject, quarantine, or deliver. A message fails DMARC if it fails both SPF and DKIM.
The manual setup cost:
Manual setup of these records takes 12-15 hours for 50 domains. You log into DNS panels, create TXT records, wait 24-48 hours for propagation, then test with Mail-Tester before campaigns can launch.
The automated alternative:
With automated infrastructure, this drops to minutes. Our video on SPF, DKIM, and DMARC setup shows the 2-minute process for configuring 10+ inboxes.
Domain strategy for cold email
Never use your primary domain:
Using your main business domain for cold emails is a fast track to ruining its reputation. Cold email domains protect your primary domain while allowing outreach campaigns at scale.
Choose the right TLDs:
Extensions like .com, .net, or .io align with professional branding. Avoid country-specific TLDs unless targeting that region.
Maintain proper inbox-to-domain ratios:
The sustainable way to scale is 2-6 inboxes per domain. By purchasing ten domains and setting up three email inboxes per domain, you can scale to 900 emails daily (10 × 3 × 30).
Inbox naming best practices
Keep usernames human. Use real names like john.smith@company.com instead of generic addresses.
Good inbox names:
john.smith@domain.com
sarah.jones@domain.com
michael.chen@domain.com
Bad inbox names:
sales@domain.com
info@domain.com
noreply@domain.com
Professional sender names build trust with both inbox providers and recipients. For more on custom domain setup, our guide on custom domains covers the technical details.
Dedicated IPs vs shared IP pools: The reputation trade-off
The type of IP address you send from determines who controls your deliverability fate. This is not a minor technical detail. It is the single biggest infrastructure decision you'll make.
How shared IPs create "noisy neighbor" problems
Shared IP pools work like carpool lanes where you're affected by other drivers. Multiple senders use the same IP address, which means the actions of one sender can impact the email deliverability and reputation of another.
The core problems with shared IPs:
Your deliverability is tied to the collective behavior of all senders sharing the IP
If another sender starts spamming or experiences high bounce rates, your email performance suffers
When ISPs spot malicious activity like phishing attacks, they add the IP address to blacklists
You have no control over who else uses the IP or how they send
A few bad "neighbors" sending spammy emails can tank your inbox placement overnight.
How dedicated IPs isolate your reputation
Dedicated IPs work like private lanes where your behavior alone determines reputation. You own the IP address. Your sending patterns, engagement rates, and complaint levels are the only factors affecting your deliverability.
Inframail provides 1 dedicated US-based IP on the Unlimited Plan ($129/month) and 3 dedicated IPs on the Agency Pack ($327/month). This isolation means client campaigns don't suffer when someone else abuses shared infrastructure.
Our video walkthrough comparing dedicated IP vs shared IP pools breaks down the technical differences and shows real-world impact on campaign performance.
"We spent months hunting for a reliable cold-emailing stack. After repeated failures with another provider, we trialled two options—Inframail and a competitor. We chose the competitor. A month later, we switched back to Inframail. Zero issues since. Rock-solid infrastructure, sharp support, genuinely dependable." - Verified user review of Inframail
Email reputation is like a credit score. The better your sender score, the more likely your email will get delivered. Each inbox service provider acts as a gatekeeper with its own algorithm that weighs reputation score and blacklist status to make delivery decisions.
How to set up cold email infrastructure for 75%+ inbox placement
Achieving consistent inbox placement requires a systematic approach across four phases: domain procurement, configuration, warmup, and volume pacing.
Step 1: Domain procurement
Purchase domains with reputable TLDs. The InfraMail Setup Tutorial shows the complete process from domain purchase through inbox provisioning.
Follow these best practices when buying domains:
Buy .com or .net extensions
Avoid cheap TLDs like .xyz or .info
Purchase through your infrastructure platform when possible for streamlined setup
Budget $6-16 per domain annually ($12 average)
Step 2: DNS configuration
Manual DNS configuration requires logging into panels like Namecheap, GoDaddy, or Cloudflare to create SPF, DKIM, and DMARC records. It can take up to 48 hours for authentication to start working as DNS changes propagate globally.
With Inframail's automated setup, DNS records configure in seconds without manual panel access.
"I can set-up inboxes in 5mins while saving money on Google Workspace subscriptions and benefit from great deliverability. All of my campaigns on Inframail are on a >10% reply rate, which is really good." - Verified user review of Inframail
Our help center article on calculating email sending capacity provides guidance on matching infrastructure to campaign requirements.
Step 3: The warmup phase
New inboxes need gradual volume increases before running campaigns. According to Saleshandy's warmup methodology, start with 30-50 emails/day, set the ramp-up rate to 5 emails/day, and run the warmup process for 3-4 weeks.
Recommended warmup approach from **Instantly's slow ramp guide:**
Week | Daily Volume | Focus |
|---|---|---|
Week 1 | Warmup only for 3 days, then 10-18/day | Establishing baseline engagement |
Week 2 | 22-25/day | Target seed placement at or above 80% |
Week 3 | 30/day if health holds | Gradual campaign introduction |
Week 4+ | Maintain 30-50/day max | Steady state operations |
Warmup emails per day should be 30 if your email account is less than six months old, but 40 if it's older.
Inframail requires external warmup tools. Our guide on how to warm up your inboxes after migrating covers the integration process. For recommended settings, watch our video on best warmup settings for Instantly.ai.
Step 4: Volume pacing
Don't send 500 emails day one. Start with 5-10 new contacts per day and never exceed 100 emails per day from a single email address.
Follow these safe sending limits:
30-50 cold emails per inbox per day once warmup complete
Keep total volume across all inboxes under 200 emails per domain daily as recommended by ScaledMail's infrastructure analysis
Hold steady at 30 or less cold emails per warmed inbox to keep risk low, especially in the first 90 days
Monitoring and maintaining infrastructure health at scale
Visibility into domain and IP health prevents client-facing fires before they start. Without monitoring, you learn about deliverability problems when angry clients call on Friday afternoon.
Dashboard requirements
Your infrastructure dashboard needs real-time visibility into four critical metrics:
Domain authentication status (SPF, DKIM, DMARC pass rates)
IP blacklist presence across major databases
Inbox health scores and warmup progression
Bounce and complaint rates by domain and campaign
Our help article on identifying if campaign emails are going to spam explains the metrics that matter and healthy benchmarks.
Blacklist monitoring and delisting
When ISPs detect malicious activity like phishing attacks or spoofing, they add IP addresses to blacklists. Tools like Sender Score, Talos, MxToolbox, and Google Postmaster Tools provide monitoring and alerts about blacklist status.
Inframail includes blacklist monitoring with auto-submitted delisting requests when domains get flagged. This automation prevents weekend emergencies from becoming Monday morning client cancellations.
Phantom redirects for tracking links
ESPs can flag tracking domains as suspicious. The phantom redirects feature hides domain redirects from inbox providers. Our help article on understanding phantom redirects explains the technical implementation.
"One of the best mailbox infra vendors I have ever used super easy and quick setup and support is practically 24/7 with at max a 2min wait to get a question answered." - Verified user review of Inframail
For troubleshooting common issues, watch our video on getting cold emails delivered and check our article on common SMTP mail issue scenarios.
Build vs buy: Comparing Google Workspace, manual SMTP, and Inframail
Different infrastructure approaches suit different situations. Here's how they compare across the factors that matter for agencies:
Factor | Google Workspace | Manual SMTP | Inframail |
|---|---|---|---|
Cost (50 inboxes) | $350-420/month platform only | Variable (domains + SMTP + warmup) | $129/month flat |
Cost (200 inboxes) | $1,400-1,680/month platform only | Variable | $129/month flat |
Setup time (50 domains) | 12-15 hours manual DNS | 12-15 hours manual | Minutes with automation |
IP type | Shared with all users | Depends on provider | 1-3 dedicated US IPs |
Best for | <10 inboxes, general business | Technical experts, tight budgets | Agencies scaling 50-200+ domains |
When each option makes sense
Google Workspace works for teams needing fewer than 10 cold email inboxes who already use Google for business operations. The per-seat pricing becomes unsustainable as inbox counts grow.
Manual SMTP setup (Amazon SES at $0.10/1,000 emails, self-managed servers) works for technical operators with more time than budget. You get maximum control but shoulder all the configuration, monitoring, and troubleshooting burden yourself.
Inframail fits agencies managing multiple clients who need predictable costs and minimal setup time. The flat-rate model means adding clients doesn't proportionally increase infrastructure spend.
"Inframail has been absolute gold in terms of delivering a great customer experience, and allowing me to spin up cold email infrastructure at scale for my clients as easily and fast as possible" - Verified user review of Inframail
For integration with your sending platform, our help doc on what email platforms work with Inframail covers compatibility with Instantly, Smartlead, and other tools.
Stop renting your reputation
Your cold email infrastructure is not a cost center to minimize. It is the foundation that determines whether campaigns reach inboxes and whether your agency maintains healthy margins.
The math favors dedicated infrastructure:
Per-seat pricing grows your infrastructure costs faster than your revenue as you scale
Shared IPs mean your deliverability depends on strangers' sending behavior
Manual DNS setup means founder hours go to configuration instead of sales
Flat-rate pricing with dedicated IPs and automated setup solves all three problems.
Sign up to Inframail and get started today. Stop paying per-seat prices for cold email. Get unlimited inboxes and dedicated IPs for $129/month.
Frequently asked questions
How many emails can I send per inbox safely?
Send 30-50 cold emails per inbox per day once warmup completes. According to Instantly's deliverability research, many teams hold at 30 or less to keep risk low.
Do I need a dedicated IP for cold email?
Yes. Dedicated IPs isolate your reputation from other senders. With shared IPs, another sender's spam can hurt your deliverability even when your own practices are perfect.
How long does DNS propagation take?
Up to 48 hours manually. Automated platforms provision records instantly with propagation completing within hours.
How many inboxes should I run per domain?
2-6 inboxes per domain is the sustainable range for scaling without reputation damage.
What inbox placement rate should I target?
Aim for seed placement at or above 80% across Gmail and Outlook addresses. Below this signals problems requiring volume reduction.
Does Inframail include email warmup?
No. Inframail requires external warmup tools like Warmbox or Instantly's warmup feature. The platform savings more than cover these costs.
Key terms glossary
SPF (Sender Policy Framework): A DNS TXT record that lists all servers authorized to send email from your domain, helping inbox providers verify sender identity.
DKIM (DomainKeys Identified Mail): A digital signature added to emails using public/private key cryptography, proving messages haven't been tampered with in transit.
DMARC (Domain-based Message Authentication, Reporting and Conformance): A policy that tells receiving servers how to handle messages failing SPF or DKIM checks.
TCO (Total Cost of Ownership): The complete cost of infrastructure including platform fees, domain costs, warmup tools, and sending platforms.
Dedicated IP: An IP address used exclusively by one sender, where reputation depends solely on that sender's behavior.
Shared IP Pool: An IP address used by multiple senders, where reputation depends on all senders' collective behavior.
DNS Propagation: The time required for DNS record changes to update across global nameservers, typically up to 48 hours.
