Cold Emailing
Jan 31, 2026
CEO and co-founder
Cold Email Infrastructure: Complete Guide to Building Scalable Sender Systems
The anatomy of a scalable cold email infrastructure stack
Cold email infrastructure isn't just "email accounts." You're building a coordinated system of four components that determine whether your messages land in inboxes or spam folders. Understanding this stack matters because each component affects your deliverability and costs differently.
1. Domain administration
You'll use sending domains separate from your main brand (like getcompanyname.com or trycompanyname.io) exclusively for outbound campaigns. Choose domains with .com extensions and incorporate your brand name with prefixes like "go," "try," or "get" to maintain credibility while protecting your primary domain reputation.
2. DNS authentication
You'll configure DNS records as the "ID card" of your email. Three protocols work together:
SPF (Sender Policy Framework): A DNS text entry showing which servers can send mail for your domain. According to technical documentation on SPF, SPF is authoritative because only domain owners can modify the main domain zone.
DKIM (DomainKeys Identified Mail): Cryptographic signatures that prove your emails haven't been tampered with during transit.
DMARC (Domain-based Message Authentication): Tells receiving servers what action to take when messages fail SPF or DKIM checks, with options to reject, quarantine, or deliver.
3. The engine (SMTP/IMAP)
SMTP handles sending while IMAP handles receiving. Your MX records direct incoming emails to your servers. Without properly configured MX records, no emails arrive. This is where your infrastructure provider (Google Workspace, Microsoft 365, or a dedicated platform) actually provisions and manages your mailboxes.
4. Reputation management
New IP addresses require warmup to establish sender reputation that inbox providers trust. Emails sent gradually avoid blocks from providers that haven't previously seen activity from your IP. This applies whether you're on shared or dedicated infrastructure.
For a complete visual walkthrough of this stack in action, watch the Ultimate Cold Email Infrastructure Guide for 2025 on our YouTube channel.
The economics of scale: When to switch from Google Workspace
The per-seat pricing model creates predictable problems as you grow. Here's the math that matters.
The per-inbox cost trap
Google Workspace Business Starter costs $7-8.40 per user per month, depending on whether you commit annually or pay monthly. Microsoft 365 Business Basic runs $6 per user per month with annual commitment. Both scale linearly with inbox count.
Here's what your infrastructure bill looks like at different scales (domain costs calculated at approximately $10/year average, amortized monthly):
Inbox Count | Google Workspace (Monthly) | Microsoft 365 Basic | Inframail (Flat Rate + Domains) |
|---|---|---|---|
50 inboxes | $350-420/month | $300/month | $129/month + domains |
100 inboxes | $700-840/month | $600/month | $129/month + domains |
200 inboxes | $1,400-1,680/month | $1,200/month | $129/month + domains |
The flat-rate model shows clear advantages at scale. For 50 inboxes, you're looking at $170-290 in potential monthly savings depending on your domain configuration.
The break-even calculation
The break-even point between per-seat and flat-rate pricing typically falls around 15-20 inboxes. Beyond that threshold, every inbox you add increases the cost gap. Annualized savings compound quickly when you run 50+ inboxes across multiple clients.
The hidden cost of labor
Infrastructure bills are only half the story. Manual DNS configuration for 50+ domains can consume significant time monthly. You're logging into Namecheap or GoDaddy, manually creating SPF records (like v=spf1 include:spf.protection.outlook.com ~all), configuring DKIM, setting DMARC policies, waiting for propagation, then testing with Mail-Tester before campaigns can launch.
According to GoDaddy's documentation, most DNS changes take effect within an hour but can take up to 48 hours to update globally. That lag time delays campaign launches and creates operational unpredictability.
The time savings compound when you eliminate this bottleneck.
When you calculate your true hourly rate, DNS work represents significant opportunity cost. Those hours could be spent on sales calls, client strategy, or building playbooks that scale.
Core components of high-deliverability infrastructure
Deliverability separates infrastructure that protects client retention from infrastructure that triggers churn. Two factors matter most: IP reputation and DNS configuration.
Dedicated vs. shared IPs
A shared IP is used by multiple senders simultaneously. Since the IP is shared, so is the sending reputation. Your deliverability rate depends not only on your behavior but on everyone else sending from that IP. If another sender uses that IP for malicious purposes like spamming, they can jeopardize your metrics.
A dedicated IP address is exclusively yours for sending emails. Your reputation is entirely in your hands, meaning deliverability depends only on your practices. No one else's mistakes drag you down.
The carpool lane analogy: Shared IPs work like carpool lanes where you're affected by other drivers. One bad actor spamming gets the whole IP range flagged. Dedicated IPs work like private lanes where your behavior alone determines reputation.
We include 1 dedicated US-based IP on the Unlimited Plan and 3 dedicated US-based IPs on the Agency Pack. This isolation protects your sending reputation from contamination by other users on shared pools.
The DNS configuration bottleneck
Manually configuring SPF, DKIM, and DMARC for 50 domains creates specific operational drag. You're working within character limits that require careful attention. For TXT records on Namecheap, the Host field caps at 60 symbols while the Value field allows 2500 symbols. These constraints force precision to avoid truncation errors.
The fastest way to achieve basic DMARC, DKIM, and SPF setup is 7 steps within 1 hour per domain, depending on DNS propagation speed. Multiply by 50 domains and you're looking at significant time investment. Typos in TXT records don't throw obvious errors. Your campaigns just quietly underperform until you diagnose the problem.
Automated DNS configuration eliminates this bottleneck entirely. Watch our Cold Email Setup: SPF, DKIM, and DMARC video showing a 2-minute setup for 10+ inboxes.
Footprint protection through redirects
Phantom redirects hide your domain forwarding from ESPs. Regular redirects appear visible in email headers, creating detectable footprint patterns across your sending domains. Phantom redirects mask this connection. Learn more in our help article on understanding the difference between normal redirects and phantom redirects.
Step-by-step: Building your infrastructure from scratch
Here's how you spin up cold email infrastructure that scales without multiplying your DNS panel hours.
Domain procurement: Purchase from reputable providers like GoDaddy or Namecheap. Domains cost $6-16 per year depending on extension and registrar. Incorporate your brand name using permutations with prefixes like "go," "try," "get," or suffixes like "emails" or "HQ." Avoid numbers, hyphens, or special symbols. Phishing attempts often use character substitution (like '0' instead of 'o'), so stick with clean alphanumeric names. Choose .com or country-specific extensions like .us or .uk. Avoid trendy extensions like .xyz, .co, or .llc, as these can trigger spam filters or dilute credibility.
Infrastructure provisioning: With automated platforms, you can purchase domains directly through the interface or transfer existing domains. The platform then auto-configures SPF, DKIM, and DMARC records without manual DNS panel work. Our How to Create Unlimited Cold Email Inboxes video demonstrates the complete process. The How to send 1000+ Cold Emails Per Day video shows the workflow for buying domains and setting up inboxes quickly.
"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; it removes friction and allows you to focus on execution rather than setup." - Verified user review of Inframail
Connecting to sending platforms: Once inboxes are provisioned, export IMAP/SMTP credentials to CSV format. Import directly to Instantly.ai, Smartlead, or other sending platforms. Check our help article on what email platforms work with Inframail for the full compatibility list. The change sender names and download CSV files guide walks through bulk credential management.
The warmup phase: You still need warmup regardless of your infrastructure provider. When starting on a new IP address, you must establish sender reputation that inbox providers trust. Emails sent gradually avoid blocks from providers that haven't seen activity from your IP. External warmup tools like Warmbox ($15-50/month per inbox) or Instantly's built-in warmup handle this process. Warmup is a specialized function requiring different technical approaches than inbox provisioning, which is why you'll typically use dedicated tools for this step. Read our guide on how to warm up your inboxes after migrating to Inframail for specific protocols.
For additional context on building cost-effective systems, watch I Built the Cheapest Cold Email Infrastructure for an operator's perspective on optimizing spend.
How to evaluate infrastructure providers without getting burned
Marketing claims from infrastructure vendors often sound identical. Here's how to cut through the noise and validate what matters.
Decision criteria framework
Use this matrix when evaluating any cold email infrastructure provider:
Criterion | Weight | What to Look For |
|---|---|---|
Cost structure | 30% | Flat rate vs. per-inbox? Calculate TCO at 50, 100, 200 inboxes including domains and warmup tools |
Setup velocity | 20% | Can you provision 10 domains in under 10 minutes? Demand unedited demos with timers visible |
IP reputation | 25% | Dedicated or shared? Do they publish their IP ranges? How is blacklist monitoring handled? |
Platform dependency | 15% | Are they reselling Google (exposes you to policy change risk) or running private Microsoft infrastructure? |
Contract flexibility | 10% | Month-to-month or forced quarterly/annual? Can you pilot 10-20 domains before committing? |
Red flags to watch
Pricing hidden behind demos: If you can't calculate ROI in 10 minutes from their website, they're counting on pressure tactics to close.
Vague deliverability claims: "Best-in-class" means nothing. Ask for Mail-Tester scores, sample sizes, and testing methodology.
Forced long-term commitments: Quarterly billing requirements before you can validate performance with real campaigns means they're locking in switching costs before proving value.
No referenceable customers: Anonymous testimonials aren't verifiable. Ask for 2-3 customers at similar scale who will take calls.
What real validation looks like
"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
"The infrastructure I've purchased has been working great for our company for the past 6 months and has been a lot better value than setting up elsewhere. The support team are quick to help with any issues or quieries." - Verified user review of Inframail
Our calculate your email sending capacity guide helps you model requirements before committing.
Platform-specific considerations
Google Workspace Business Starter caps at 300 users, which matters if you're scaling aggressively. The web-only restriction on Basic plans limits workflow flexibility.
Microsoft infrastructure advantage: We're built on Microsoft's cloud platform with an enterprise partnership announced in January 2024. This provides infrastructure stability and dedicated US-based IPs rather than shared pools.
"A smart team of young founders building a genuinely impressive product. I've tried quite a few email hosting platforms and Inframail consistently has the best delivery AND the best prices." - Verified user review of Inframail
"Been using Inframail for 2+ years now... Pretty solid deliverability compared to other platforms I've used in the past." - Verified user review of Inframail
For sending strategies that complement solid infrastructure, the How To Send Cold Emails That Inbox video covers 2 million+ email campaigns with infrastructure setup context.
Your infrastructure checklist before committing
Before committing to any cold email infrastructure, verify these items:
Cost validation:
Calculate total cost at your target inbox count (platform + domains + warmup)
Compare against current Google Workspace or Microsoft 365 spend
Model cost trajectory at 50, 100, and 200 inboxes
Technical verification:
Confirm IP type (dedicated vs. shared)
Verify DNS auto-configuration capabilities
Check sending platform compatibility (Instantly, Smartlead, etc.)
Understand warmup requirements and costs
Operational fit:
Test setup speed with 5-10 domains before full commitment
Verify support response times and quality
Confirm month-to-month flexibility exists
Request customer references at similar scale
"K and the team are always there to help. The technical set up of hosting and seeing cold email can be daunting as there are a lot of items to consider and manage. I've had nothing but excellent service and the team showing a commitment to help every time I've contacted support." - Verified user review of Inframail
"I've been using Inframail for a couple of months and the experience has been really good. 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
Ready to cut your infrastructure costs?
Sign up to Inframail and get started today. Our Unlimited Plan runs $129/month for unlimited inboxes with 1 dedicated IP. No per-seat charges. No manual DNS configuration.
For questions before signing up, check the Frequently Asked Questions about Inframail or watch the full cold email setup walkthrough.
Frequently asked questions
Here are specific answers to the most common infrastructure questions we get from agency founders:
How many inboxes do I need per client?
Inbox requirements vary by sending volume. For campaigns sending 50-100 emails per inbox per day, 10 inboxes supports 500-1,000 daily sends per client.
What's the actual setup time difference between manual and automated?
Manual DNS configuration takes significant time per domain plus propagation delays of up to 48 hours. Automated platforms provision inboxes rapidly with DNS configured automatically.
Do I need separate warmup tools with Inframail?
Yes. Infrastructure provisioning and warmup are separate functions. Use Warmbox ($15-50/month per inbox) or Instantly's built-in warmup feature to establish sender reputation before full-volume campaigns.
Can I use Inframail with Google Workspace?
No. We provide Microsoft-based infrastructure exclusively with dedicated IPs. If you specifically require Google Workspace for your workflows, Inframail isn't the right fit. If you need dedicated IP infrastructure that isolates your reputation, we're purpose-built for that.
What happens if my IP gets blacklisted?
Our deliverability monitoring dashboard tracks domain and IP health with blacklist monitoring. The platform monitors for blacklist additions and can assist with delisting requests when domains are flagged.
How does flat-rate pricing work with unlimited inboxes?
The $129/month Unlimited Plan includes 1 dedicated IP and unlimited inbox creation. You pay separately for domains ($6-16/year each) but inbox provisioning carries no additional per-seat fees regardless of volume.
Key terms glossary
SPF (Sender Policy Framework): A DNS text record listing servers authorized to send email for your domain. Receiving servers check SPF to verify sender legitimacy.
DKIM (DomainKeys Identified Mail): Cryptographic signatures added to outgoing emails that verify the message hasn't been modified during transit.
DMARC (Domain-based Message Authentication): A policy record telling receiving servers what to do when emails fail SPF or DKIM checks. Options include reject, quarantine, or deliver with a report.
SMTP (Simple Mail Transfer Protocol): The protocol used to send emails between servers. SMTP credentials are required to connect your inboxes to sending platforms.
IMAP (Internet Message Access Protocol): The protocol used to receive and manage emails on servers. IMAP keeps messages on the server, allowing access from multiple devices.
Dedicated IP: An IP address used exclusively by one sender. Reputation depends only on that sender's behavior.
Shared IP: An IP address used by multiple senders simultaneously. Reputation is affected by all users on that IP.
MX Record: DNS records specifying which mail servers receive email for a domain. Without correct MX records, incoming emails fail to deliver.
