Cold Emailing
Feb 5, 2026
CEO and co-founder
Cold Email Infrastructure for Agencies: Scaling from 50 to 500+ Domains
The hidden margin killer: Why per-inbox pricing fails at scale
Google Workspace Business Starter costs $7-8.40 per user per month depending on whether you commit annually or pay monthly. At 20 inboxes, that's $140-168/month. Manageable. But watch what happens as you scale:
Inbox Count | Google Workspace (Annual) | Inframail Unlimited | Monthly Savings |
|---|---|---|---|
50 inboxes | $350/month | $129/month | $152.50/month |
100 inboxes | $700/month | $129/month | $434/month |
200 inboxes | $1,400/month | $129/month | $997/month |
500 inboxes | $3,500/month | $129/month | $2,686/month |
The Inframail Unlimited Plan stays at $129/month whether you create 50 or 500 inboxes. Add domain costs ($5-16 each through the platform) and you're looking at approximately $163/month total for 50 inboxes compared to $350-420/month on Google Workspace.
That's $1,830-2,670 in annual savings per 50 inboxes. For an agency running 200 inboxes across 10-15 clients, the difference compounds to over $11,900 annually.
"So affordable that it will make your unit economics work, even for lower ticket b2b businesses like ours." - Verified user review of Inframail (Inframail now has [38 5-star reviews on Trustpilot](https://www.trustpilot.com/review/inframail.io).)
The linear cost trap hits hardest between 50 and 200 domains. This is exactly when agencies need capital to hire their first account manager or invest in lead generation. Instead, that budget disappears into infrastructure overhead that delivers zero competitive advantage.
Core components of a scalable cold email infrastructure
Before diving into scaling milestones, you need to understand the four components that determine whether your infrastructure can grow with your agency.
Domain authentication (SPF, DKIM, DMARC)
These three protocols prove to receiving servers that your emails are legitimate and authorized:
SPF (Sender Policy Framework): A DNS TXT record listing IP addresses authorized to send email from your domain
DKIM (DomainKeys Identified Mail): A cryptographic signature proving the email wasn't altered in transit
DMARC (Domain-based Message Authentication): A policy telling receivers how to handle emails that fail SPF or DKIM checks
For a detailed walkthrough on setting these up in seconds rather than hours, watch our SPF, DKIM, and DMARC setup tutorial showing the 2-minute process for 10+ inboxes.
Manual configuration means logging into DNS panels, creating records, waiting for 24-48 hours of propagation time, and testing with Mail-Tester. At scale, this becomes the primary bottleneck.
Sending nodes (the inboxes themselves)
Your inboxes live on either Microsoft or Google infrastructure. Each has trade-offs. Recent deliverability data from Q1 2025 shows Gmail averaging 53.70% inbox rates while Exchange (Office365) dropped to 50.70%.
The choice isn't just about deliverability. It's about ecosystem integration, sending limits (Google allows 2,000 emails/day versus Microsoft's 1,000), and how your sending platform connects to these mailboxes.
Reputation management
Warmup tools and blacklist monitoring determine whether your domains survive their first 30 days. New domains need 2-4 weeks minimum of warmup before running campaigns. Our warmup guide covers the full process.
Blacklist monitoring catches problems before clients notice. When a domain gets flagged, you need alerts within hours, not days.
IP architecture (dedicated vs. shared)
This is where agencies make or break their deliverability at scale. Shared IP addresses mean multiple users send from the same IP, and the reputation is collectively influenced by everyone using it.
Think of shared IPs like carpooling. If one passenger misbehaves, everyone in the car faces consequences. One bad sender can damage deliverability for all users on that IP pool.
Dedicated IPs give you complete control. Your sending behavior alone determines reputation, and you're not affected by other senders' spam complaints or poor list hygiene.
The agency scaling roadmap: Infrastructure milestones
Each growth phase introduces specific challenges that require different solutions. Here's what to expect and how to prepare.
Phase 1: 50 domains (stabilizing costs and workflows)
The challenge: At 50 domains, manual DNS configuration consumes 12-15 hours monthly. You're logging into Namecheap or GoDaddy to manually create SPF, DKIM, and DMARC records for each domain, waiting for propagation, and testing before campaigns can launch. Meanwhile, Google Workspace bills hit $350-420/month.
The operational reality: Every new client means 3-5 domains to configure. That's 45-90 minutes of DNS work before you can even think about the actual campaign. Add warmup time (2-4 weeks per inbox according to Microsoft's warmup guidance) and new client onboarding stretches to 3-4 weeks.
The fix: Move to flat-rate infrastructure to cap costs and automate DNS setup.
With Inframail, domain purchased → DNS auto-configured → inbox provisioned → credentials exported in minutes.
For a complete walkthrough, watch our Ultimate Cold Email Infrastructure Guide covering the full setup process.
Phase 2: 100-250 domains (automating DNS and provisioning)
The challenge: Client churn (typical 10-20% monthly in agency world) creates constant domain rotation needs. At 150 domains, you might decommission 15-30 domains monthly while adding 20-40 new ones. Manual provisioning becomes impossible to maintain.
Cold email infrastructure at this scale requires advanced safeguards like multi-domain rotation and automated management. The reactive "fire drill" environment takes over. Client churns, emergency deprovisioning needed. New client signs, rush to set up infrastructure. Domain gets flagged, panic to diagnose.
The operational reality: Many tools cap sending accounts per seat, forcing you to buy more seats just to manage deliverability across multiple inboxes. Per-seat pricing models eat into margins exactly when you need capital for growth.
The fix: Bulk domain management and instant inbox provisioning.
"I personally have over 1,000 email accounts with Inframail for one flat price. Adding all those records would have probably taken dozens of hours. Instead all records were added within 10 minutes." - Verified user review of Inframail
The ability to export credentials as CSV and bulk-import to Instantly or Smartlead eliminates the bottleneck entirely. Watch the Inframail 3.5 demo showing how to create unlimited inboxes instantly.
Phase 3: 500+ domains (dedicated IPs and governance)
The challenge: At enterprise scale, the single biggest threat is a global deliverability collapse triggered by one client's poor practices affecting your entire infrastructure.
Being put on a blacklist can cost a company its entire email deliverability rate. When a domain or IP is blacklisted, emails end up in spam folders instead of inboxes. At 500+ domains, if you're on shared infrastructure, one bad actor can impact hundreds of client campaigns simultaneously.
The operational reality: Manual oversight becomes impossible. You need automated monitoring, segmented sending infrastructure, and clear governance policies for client list quality. The psychological shift is significant. You're no longer managing infrastructure. You're managing risk.
The fix: Isolate client reputation using dedicated IPs.
The Inframail Agency Pack includes 3 dedicated US-based IPs, allowing you to segment clients strategically:
IP #1: High-risk clients or new, untested campaigns
IP #2: Stable, established clients with good engagement history
IP #3: Medium-risk clients or testing new approaches
If one client's campaign goes wrong (poor list quality, high bounce rates, spam complaints), others stay unaffected. This is the foundation of antifragile infrastructure.
"Rock-solid infrastructure, sharp support, genuinely dependable." - Verified user review of Inframail
For a deep dive into the dedicated vs. shared debate, watch our Dedicated IP vs Shared IP comparison.
Dedicated IPs vs. shared pools: Protecting your reputation
The IP architecture decision becomes critical as you scale past 100 domains. Let me be direct about the trade-offs.
Shared IP pools (used by some providers) mean your email deliverability depends on the sending habits of others. If other senders use that IP for spamming, they jeopardize your metrics even if you've done everything right.
Dedicated IPs give you complete control. Internet Service Providers evaluate your emails solely based on your own sending habits. You're not punished for other senders' mistakes.
The "private lane" analogy works well here. Shared IPs are carpool lanes where you're affected by other drivers. One bad actor spamming gets the whole range flagged. Dedicated IPs work like private lanes where your behavior alone determines reputation.
Our Unlimited Plan includes 1 dedicated US-based IP. The Agency Pack includes 3 dedicated IPs for agencies running larger portfolios. This lets you isolate risk across client segments without the $327/month minimums or approval gatekeeping some providers require.
"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
Building antifragile infrastructure to prevent deliverability collapse
"Antifragile" means systems that don't just resist failure but actually benefit from stressors. In cold email context, this means your infrastructure maintains performance even when individual components fail.
Traditional infrastructure collapses when stressed. One bad client ruins deliverability for all. Resilient infrastructure absorbs the hit but doesn't grow stronger. Antifragile infrastructure uses stress as feedback. Failed domains are replaced, problem clients are isolated, and the system adapts.
Key features that enable antifragility
1. Automated DNS setup eliminates human error
Manual configuration introduces mistakes. A typo in an SPF record, a forgotten DMARC policy, a misconfigured DKIM signature. Automation handles all of it in seconds per domain.
2. Deliverability monitoring catches problems early
Track domain and IP health with blacklist monitoring. The platform can auto-submit delisting requests when domains are flagged. Read more about understanding healthy metrics.
3. Phantom redirects protect domain reputation
Understanding the difference between normal redirects and phantom redirects helps you hide domain redirects from ESPs that might otherwise flag your sending patterns.
4. Domain rotation enables rapid recovery
By enabling agencies to quickly deploy and rotate through domains, the system can adapt to stress by shifting load to healthy infrastructure. When a domain gets blacklisted, you swap it out in minutes rather than days.
For practical implementation, watch our video on how to actually get cold emails delivered.
Vendor comparison: Inframail vs. Google Workspace vs. shared IP providers
Here's an objective breakdown of when to use each option:
Factor | Inframail | Google Workspace | Shared IP Providers |
|---|---|---|---|
Cost (100 inboxes) | $129/month flat | $700-840/month | $190-275/month |
IP Type | Dedicated (1-3) | N/A (Google infrastructure) | Shared pool |
DNS Automation | Yes (seconds per domain) | No (manual) | Varies |
Setup Time | Minutes | Hours per domain | 10-30 minutes |
Reputation Risk | Isolated | Isolated | Contagion from other users |
When Google Workspace makes sense:
Under 20 inboxes for cold email
Need Google ecosystem integration (Sheets, Drive, Meet)
Running internal company email alongside cold outreach
When Inframail makes sense:
50+ inboxes for dedicated cold email
Need flat-rate predictability for agency margins
Want dedicated IPs for reputation isolation
Require fast provisioning for client onboarding
"Inframail was recommended to me by a friend over two years ago. I've been using them ever since. Don't look back. Pretty solid deliverability compared to other platforms I've used in the past." - Verified user review of Inframail
Read more about unlimited email hosting options in our detailed comparison.
5-step checklist to migrate and scale your infrastructure
Use this framework to transition from Google Workspace (or manual setup) to automated, flat-rate infrastructure.
Step 1: Audit your current spend
Calculate your true infrastructure costs:
Google Workspace: Count total inboxes × $7-8.40/month
Warmup tools: Count active inboxes × $15-50/month
Sending platform: Monthly subscription
Domain costs: Annual cost ÷ 12
Add these together. If the total exceeds $163/month for 50 inboxes, you're overpaying for infrastructure.
Step 2: Purchase domains separately from your main brand
Buy secondary domains specifically for cold outreach. Never use your primary business domain for cold email. Our domain guide covers best practices for domain selection and setup.
Recommended ratio: 1 domain per 2-5 inboxes for optimal deliverability spread.
Step 3: Connect domains to Inframail for auto-DNS
Link your domain registrar to the platform. The automation handles SPF, DKIM, DMARC, email forwarding, and domain redirects in seconds.
"InfraMail makes it remarkably easy to purchase domains, configure them correctly, create inboxes, and initiate warm-up immediately." - Verified user review of Inframail
Step 4: Provision inboxes and export credentials
Create unlimited inboxes under your plan. Export credentials as CSV including email, password, and IMAP/SMTP settings. This file uploads directly to Instantly, Smartlead, or other platforms. See what platforms work with Inframail.
Step 5: Start warmup before launching campaigns
Begin warmup using your preferred tool. Achieving maximum deliverability takes 2-8 weeks depending on volume targets. Our warmup migration guide covers the full process.
For a complete visual walkthrough, watch InfraMail Setup Tutorial from Shivam Gupta showing the step-by-step process.
Ready to scale without the margin squeeze?
The agencies that grow past $1M ARR aren't the ones with the best cold email copy. They're the ones who eliminated infrastructure as a bottleneck. Flat-rate pricing, automated DNS, and dedicated IPs turn infrastructure from a cost center into a competitive advantage.
Sign up to Inframail and get started today. Your infrastructure bill stays at $129/month whether you're running 50 inboxes or 500.
FAQs
How much does Inframail cost compared to Google Workspace for 100 inboxes?
Inframail costs $129/month flat for unlimited inboxes. Google Workspace Business Starter costs $700-840/month for 100 inboxes at $7-8.40 per user. Annual savings: $5,208-6,888.
How long does DNS setup take with automated configuration?
Seconds per domain. Manual setup takes approximately 15-18 minutes per domain. For 50 domains, that's 12-15 hours saved monthly.
Do I need a separate warmup tool with Inframail?
Yes. Inframail provides infrastructure (inboxes and DNS). You'll need external warmup tools like Warmbox or Lemwarm at $15-50/month per inbox unless you're on the DFY package which includes warmup.
What sending platforms integrate with Inframail?
Inframail exports IMAP/SMTP credentials as CSV files compatible with Instantly, Smartlead, Lemlist, and other SMTP-based sending platforms.
How many dedicated IPs do I get?
Unlimited Plan includes 1 dedicated US-based IP. Agency Pack includes 3 dedicated US-based IPs for client segmentation.
How long before new inboxes can start sending campaigns?
Warmup takes 2-4 weeks minimum to establish baseline reputation. For maximum deliverability and higher volumes, plan for 4-8 weeks of warmup.
Key terms glossary
SPF (Sender Policy Framework): A DNS record that lists which IP addresses can send email from your domain. Receiving servers check this to verify sender legitimacy.
DKIM (DomainKeys Identified Mail): A cryptographic signature attached to emails proving the message wasn't altered in transit. Requires a public key stored in DNS.
DMARC (Domain-based Message Authentication): A policy telling receiving servers how to handle emails that fail SPF or DKIM checks. Options include none, quarantine, or reject.
Dedicated IP: An IP address used exclusively by your account. Your sending behavior alone determines its reputation with email providers.
Shared IP Pool: An IP address used by multiple senders. Reputation is collectively influenced by all users, creating contagion risk if one sender engages in poor practices.
DNS Propagation: The time required for DNS record changes to spread across internet servers. Typically 24-48 hours for full propagation.
Inbox Placement Rate: The percentage of sent emails that land in the primary inbox rather than spam, promotions, or being blocked entirely.
