Cold Emailing
Feb 13, 2026
CEO and co-founder
What is cold email infrastructure? Definition, components & why agencies need it
What is cold email infrastructure? The technical definition
We define cold email infrastructure as the full stack of technical pieces, tools, and processes that make cold email outreach possible and effective at scale. As Aerosend's infrastructure guide puts it, infrastructure includes "the domains you send from, DNS authentication, mailbox setup, IP reputation, sending patterns, and the systems that protect your deliverability at scale."
The critical distinction here is between infrastructure and sending platforms. According to Supersend's complete guide, "Sequencers like Instantly, Smartlead, or Apollo help you send emails, automate follow-ups, rotate domains, and manage campaigns. They do not provide the underlying reputation that determines inbox placement."
Think of it this way: if your sending platform is the engine of your outbound operation, infrastructure is the road, fuel system, and safety features that get your emails where they need to go without breaking down.
Infrastructure vs sending platform breakdown
We break down the distinction this way:
Component | Infrastructure | Sending Platform |
|---|---|---|
Purpose | Determines if emails get delivered | Determines when and how emails get sent |
Examples | Domains, DNS records, IPs, mailboxes | Instantly, Smartlead, Apollo, Lemlist |
Primary metric | Inbox placement rate | Campaign automation |
Ownership | You control reputation | You control sequences |
For a deeper dive into infrastructure setup, watch our Ultimate Cold Email Infrastructure Guide for 2025 on YouTube.
Core technical components of cold email infrastructure
Cold email infrastructure has five interconnected components. Weakness in any single piece tanks your entire deliverability. I'll break down each component with the technical details you need.
Dedicated sending domains
Your sending domain is the foundation of your infrastructure. Woodpecker's infrastructure guide is direct about this: "Sending your first cold outreach from your primary domain is the classic rookie mistake. Protect your main brand by spinning up a secondary domain or, better yet, multiple domains dedicated to cold email campaigns."
Why multiple domains? Because email service providers evaluate sender reputation at the domain level. If one domain gets flagged, you need others to maintain campaign velocity.
Domain quantity benchmarks based on operation size:
Small operations (1-3 clients): 8-20 domains
Agencies (5-15 clients): 20-50 domains
Large outbound teams (15+ clients): 50-200+ domains
According to Instantly's infrastructure breakdown, "A safe benchmark is 20-40 domains with 2-3 inboxes each. This lets you distribute volume evenly, so no single domain risks getting flagged or burned."
When purchasing domains, stick with reputable registrars and avoid expired domains. The domain name should relate closely to your primary brand so prospects can identify you. Through our platform, we handle all DNS configuration automatically once you purchase or transfer domains.
"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
DNS authentication records: SPF, DKIM, and DMARC
DNS records are the authentication layer that proves your emails are legitimate. Without proper DNS configuration, inbox providers have no way to verify that emails actually come from authorized sources. Infraforge's DNS setup guide explains each record type:
SPF (Sender Policy Framework): "SPF is like a gatekeeper for your domain. It specifies which mail servers are allowed to send emails on your behalf. When an email is sent, the recipient's mail server checks the SPF record to see if the sending server matches the list of authorized servers."
DKIM (DomainKeys Identified Mail): According to Mailstand's authentication guide, "DKIM takes security one stage further, effectively allowing you to digitally sign each message you send, proving its authenticity. The information is provided as a TXT file on the domain panel."
DMARC (Domain-based Message Authentication, Reporting & Conformance): Mailforge's DNS basics describes DMARC as "the overseer, coordinating SPF and DKIM. It tells receiving servers how to handle emails that fail SPF or DKIM checks."
Manual DNS configuration takes 15-30 minutes per domain according to Mailforge's domain setup guide. For 50 domains, that adds up to significant hours of work. You're logging into Namecheap or GoDaddy, creating SPF records (v=spf1 include:spf.protection.outlook.com ~all), adding DKIM keys, configuring DMARC policies, waiting 24-48 hours for propagation, then testing with Mail-Tester. We automate all of this.
For a quick walkthrough on automated DNS setup, check out our video on SPF, DKIM, and DMARC configuration in under 2 minutes.
"Love the fact that I don't have to deal with DNS stuff. Their support is always available, and ready to help." - Verified user review of Inframail
Email inboxes and sending limits Inframail has 38 5-star reviews on Trustpilot.
Inboxes are where your emails actually originate. The number of inboxes you operate, and how you distribute sending volume across them, directly impacts deliverability.
Salesforge's infrastructure page explains the core constraint: "Sending more than 30 to 50 cold emails per day from a single mailbox increases the risk of spam flags, blacklisting, or even full account suspension, especially on platforms like Google Workspace or Microsoft 365."
Safe sending limits per inbox:
According to MailReach's sending guide, the recommended limit is approximately 100 cold emails per day per inbox for properly warmed accounts. More conservative approaches suggest 30-50 emails per inbox, which Salesforge recommends as a starting point.
Conservative approach: 30-50 cold emails per day per inbox
Warmed accounts: Up to 100 per day per inbox
Per domain total: Less than 200 emails per day across all inboxes
The Scaledmail inbox ratio guide recommends 2-6 inboxes per domain as "the sweet spot for balancing sending volume with a healthy domain reputation."
Our flat-rate pricing lets you create unlimited inboxes for $129/month platform fee regardless of volume. For details on calculating your sending capacity, see our help article on choosing the right plan.
"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
Email warmup tools and sender reputation
New domains and inboxes have zero sending reputation. Warmup tools build that reputation by simulating natural email activity before you launch campaigns.
Mailivery's documentation explains the mechanism: "Mailivery uses AI to interact with real emails behind the scenes in your inbox. The algorithm removes your emails from SPAM and positively replies to them to improve your deliverability in real time."
How warmup works:
Sends warmup emails to a network of real inboxes
Opens and engages with those emails
Moves emails out of spam/promotions into primary inbox
Generates replies to simulate positive engagement
Builds domain reputation through consistent activity
Apollo's warmup documentation provides specific parameters: "Progressive warmup: Gradually increase email volume over time. Apollo recommends a minimum two-week time frame for the best results. Minimum: 10 emails/day. Maximum: 40 emails/day."
The Topo.io sending limits guide notes that "this process typically takes 2-4 weeks at a minimum, but can take up to 12 weeks for a domain to be considered fully mature."
Critical insight: Warmup isn't a one-time event. Stopping warmup after initial setup makes your sending pattern irregular, which can reduce deliverability scores. Keep warmup running before, during, and after campaigns.
For guidance on warmup after migration, see our help article on warming up inboxes.
IP addresses: dedicated vs shared
Your IP address is the numerical identifier that inbox providers use to track your sending behavior. There are two types: dedicated IPs (assigned exclusively to you) and shared IP pools (used by multiple senders).
GMass's infrastructure services analysis describes dedicated cold email infrastructure providers as "specialized setups that help outreach pros send out high volumes of messages while circumventing the major email platforms. Really, these services are creating their own email platform, like a private version of Google Workspace or Outlook 365."
Dedicated IP advantages:
Your sending behavior alone determines reputation
No contamination from other users' bad practices
Full control over IP warming and reputation building
Shared IP risks:
Other users' spam complaints affect your deliverability
One bad actor can get the entire IP range flagged
Limited control over reputation factors
Our video on Dedicated IP vs Shared IP Pools for Cold Email covers this distinction in detail.
We provide dedicated US-based IPs: 1 dedicated IP on our Unlimited Plan ($129/month) and 3 dedicated IPs on our Agency Pack ($327/month). Your sending reputation stays isolated from other users.
How cold email infrastructure differs from standard business email
Standard business email hosting (Google Workspace, Microsoft 365) is designed for internal communication and general business correspondence. Cold email infrastructure is purpose-built for outbound prospecting at scale. The differences are substantial.
Sending limits and cost structure
Salesforge's sending guide breaks down provider limits: "Gmail (free) allows 500 emails/day, Google Workspace permits 2,000, and Office 365 caps at 10,000/day."
These limits sound generous until you factor in the per-seat pricing model. Google Workspace Business Starter runs $7/month (annual) or $8.40/month (flexible billing) per user according to current Google Workspace pricing. Microsoft 365 Business Basic is $6/month currently.
Provider | Cost Per Inbox | 50 Inboxes | 100 Inboxes | 200 Inboxes |
|---|---|---|---|---|
Google Workspace Business Starter | $7-8.40/month | $350-420/month | $700-840/month | $1,400-1,680/month |
Microsoft 365 Business Basic | $6/month | $300/month | $600/month | $1,200/month |
Our Unlimited Plan (platform fee) | $129/month flat | $129/month | $129/month | $129/month |
For agencies managing 50+ inboxes, the platform fee difference alone reaches $221-291/month compared to Google Workspace, or $2,652-3,492 annually.
Margin impact calculation:
For an agency with 8 clients at $3,000 average monthly retainer ($24,000 total billings), infrastructure represents:
Google Workspace (50 inboxes): $385/month ÷ $24,000 = 1.6% of billings
Our Unlimited Plan (50 inboxes): $129/month ÷ $24,000 = 0.54% of billings
At 15 clients ($45,000 billings) with 100 inboxes: Google Workspace hits $770/month (1.7%), our platform stays at $129/month (0.29%)
This percentage gap directly protects the 15-20% net margins agencies need to stay viable.
Purpose and design priorities
Standard email hosting prioritizes reliability, security, and compliance with general business communication needs. Cold email infrastructure prioritizes:
Deliverability to external recipients who didn't opt in
Reputation management across multiple domains
Volume distribution to avoid triggering spam filters
Rapid scaling without linear cost increases
TrulyInbox's infrastructure overview notes that cold email infrastructure includes "authentication records such as SPF, DKIM, DMARC, and BIMI" as core components, not optional add-ons.
Watch Jasper Aiken's full cold email setup video for a practical walkthrough of how infrastructure connects to sending platforms like Instantly.
Why cold email infrastructure matters for deliverability
Deliverability is the percentage of emails that reach the inbox (not spam or promotions). Without proper infrastructure, your campaigns hit an invisible ceiling.
The deliverability gap
Supersend's guide quantifies the difference: "Teams without proper infrastructure see deliverability rates drop from 95% to under 50% within 3-6 months of scaling, while teams with infrastructure-first setups maintain 90%+ inbox placement rates."
Mailforge's daily sending guide adds context: "Senders with strong reputation metrics can achieve inbox placement rates of 95% or more, while those with poor reputations may see deliverability drop below 50%."
The math on this is stark. If you're sending 1,000 cold emails daily:
90% inbox rate: 900 emails reaching prospects
50% inbox rate: 500 emails reaching prospects
Net difference: 400 potential conversations lost daily
For an agency billing $4,000/month per client on meeting volume, that's the difference between hitting quotas and facing churn conversations. When infrastructure spend exceeds 25% of billings, you can't afford to lose 40% of your delivery capacity.
Reputation factors that infrastructure controls
Infrastructure directly controls:
Domain age and history through proper domain provisioning
Authentication status through automated DNS configuration
IP reputation through dedicated vs shared IP selection
Sending patterns through volume distribution across inboxes
Engagement signals through warmup activity
Topo.io's safe sending limits guide emphasizes complaint rates: "Keep spam complaint rate below 0.1%. This is the ultimate reputation killer."
For practical guidance on monitoring deliverability, see our help article on identifying spam issues and healthy metrics.
"Outstanding deliverability backed by personable, professional support. 1 on 1 with co-founder was extremely helpful to learning more about deliverability and proper infrastructure set up." - Verified user review of Inframail
Gmail and Yahoo compliance requirements for 2025
In February 2024, Gmail and Yahoo implemented new requirements for bulk senders. These requirements have teeth, and non-compliant emails now face rejection.
The requirements
HigherLogic's breakdown summarizes: "Gmail and Yahoo require bulk senders (those who send more than 5,000 messages in one day) to: Authenticate their email following established best practices like SPF, DKIM, and DMARC. Enable easy unsubscription: Bulk senders must ensure an easy one-click unsubscribe process and honor unsubscribes within two days."
SecurityBoulevard's 2025 update confirms enforcement status: "As of November 2025, these requirements have been enforced, with Google stating that non-compliant emails will face temporary and permanent rejections."
Specific thresholds from EmailWarmup.com's guide:
Spam complaint rate must stay below 0.3% (Google recommends under 0.1%)
SPF, DKIM, and DMARC authentication mandatory
One-click unsubscribe required
Unsubscribe requests honored within 2 days
Enforcement timeline
HigherLogic documented the rollout:
February 2024: Bulk senders who don't meet requirements started getting temporary errors on a small percentage of non-compliant traffic
April 2024: Started rejecting a percentage of non-compliant email traffic, gradually increasing rejection rate
November 2025: Full enforcement with permanent rejections
Proper infrastructure with automated DNS configuration ensures compliance. Manual setup increases the risk of misconfiguration that triggers rejection.
Why agencies specifically need dedicated cold email infrastructure
Lead generation agencies face unique challenges that make infrastructure investment essential. You're managing multiple clients, each with distinct campaigns, domains, and reputation profiles.
I've seen this pattern dozens of times. Agencies hit 5-8 clients, infrastructure costs start climbing faster than revenue, and suddenly they're burning 15 hours weekly on DNS panels instead of sales calls. The unit economics break at exactly the moment growth should accelerate.
Multi-client management complexity
Infraforge's agency guide explains: "Agencies need setups that can handle large sending volumes, protect domain reputation across multiple clients, and keep deliverability steady without constant fixes."
The same guide adds: "The platform solves a common pain point for agencies: maintaining high deliverability rates while managing the heavy email volumes that come with multi-client campaigns."
When you're sending on behalf of 5-15 clients simultaneously, you need:
Separate domain pools per client to isolate reputation
Dedicated tracking for each client's deliverability metrics
Bulk provisioning to onboard new clients quickly
Credential management across hundreds of inboxes
The cost structure problem
Supersend's agency pricing analysis highlights the margin squeeze: "Your pricing must cover the hard costs of 50+ domains, 100+ inboxes, warmup tools, and deliverability monitoring per client."
Agency infrastructure costs with traditional providers:
Cost Component | Per-Client (Traditional) | Per-Client (Flat-Rate) |
|---|---|---|
Domains (10) | $100-160/year | $100-160/year |
Email hosting (30 inboxes) | $180-252/month | Included in platform fee |
Warmup tools | External cost | External or DFY option |
Sending platform | $77-197/month | External |
Monthly hosting difference | $180-252 | $0 (covered by $129 flat fee) |
The difference compounds as you add clients. Per-inbox pricing destroys margins at scale.
Cross-contamination risk
Supersend's guide warns: "Failing to explicitly bill for the true cost and labor involved in managing dozens of domains, inboxes, and their associated technical records leads to reusing infrastructure across clients, creating massive cross-contamination risk."
Dedicated infrastructure with proper client isolation prevents one client's deliverability issues from affecting your entire portfolio.
"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
Watch our interview with $1M Agency Owner Dillon Andrew for insights on scaling agency infrastructure.
Industry benchmarks: costs, timelines, and scale
Understanding typical costs and timelines helps you budget accurately and set realistic expectations.
Infrastructure cost benchmarks
Reachoutly's agency pricing analysis provides context: "Cold email agencies charge $2,500-$15,000 monthly compared to email marketing services ranging from $500-$3,000 monthly."
Typical agency infrastructure costs:
Domains: $16.44 per domain annually from most registrars
Email hosting: $6-8.40 per inbox monthly (traditional) or $129/month flat platform fee
Warmup tools: $12-50 per inbox monthly
Sending platform: $37-197/month depending on features
Timeline benchmarks
Based on research data from Mailforge's domain setup guide, expect these timelines:
Activity | Traditional Setup | Automated Setup |
|---|---|---|
Domain purchase | Variable | Minutes |
DNS configuration | 15-30 min per domain | Automatic |
Inbox provisioning | Variable per provider | Minutes for bulk |
Warmup period | 2-4 weeks minimum | 2-4 weeks minimum |
Full maturity | 8-12 weeks | 8-12 weeks |
For a practical demonstration, watch How to send 1000+ Cold Emails Per Day using Inframail showing 5 domains and 10 inboxes configured in 4 minutes.
Risks, limitations, and honest trade-offs
No infrastructure solution is perfect. Understanding the limitations helps you plan accordingly.
What dedicated infrastructure doesn't solve
Bad targeting: Infrastructure gets emails delivered but can't fix irrelevant messaging
Poor copy: High inbox rates mean nothing if prospects don't engage
List quality: Sending to invalid emails damages reputation regardless of infrastructure
Compliance issues: Infrastructure automates authentication but doesn't ensure content compliance
Warmup dependency
Most dedicated infrastructure platforms (including ours) don't include built-in warmup tools on self-service plans. You'll need external warmup services at $12-50/month per inbox. Factor this into your TCO calculation.
Our Done-For-You package ($299/month) includes warmup, but the self-service Unlimited Plan ($129/month) requires external warmup tools.
Platform constraints
We run on Microsoft infrastructure. This works well for most outbound campaigns, but if your targets specifically filter based on Google Workspace IPs, you may need a hybrid approach.
We're also US-based infrastructure only, which matters for agencies with EU/APAC data residency requirements.
"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." - Verified user review of Inframail
Getting started with cold email infrastructure
If you're ready to build or upgrade your infrastructure, here's how we recommend you start:
Calculate your volume requirements using our sending capacity calculator
Determine domain count: Plan for 2-3 inboxes per domain, 30-50 emails per inbox daily as a conservative baseline
Budget for warmup: Factor $12-50/month per inbox for external warmup
Choose infrastructure provider: Compare flat-rate vs per-inbox pricing at your scale
Allow warmup time: Don't launch campaigns until 2-4 weeks post-setup
Sign up to Inframail and get started today. Unlimited inboxes for $129/month platform fee, automated DNS configuration, dedicated US-based IPs, and 16 hours of daily support. Built for agencies managing 50-200 domains across multiple clients.
"Been using Inframail for 2+ years now... Don't look back. Pretty solid deliverability compared to other platforms I've used in the past." - Verified user review of Inframail
FAQs
How many domains do I need for cold email?
Plan for 20-50 domains for agency operations based on Instantly's benchmarks. Use 2-3 inboxes per domain, sending 30-50 emails per inbox daily for safe volume distribution.
How long does email warmup take?
Minimum 2-4 weeks before launching campaigns according to Topo.io's guide. Full domain maturity takes 8-12 weeks. Keep warmup running continuously for best results.
What's the maximum safe sending limit per inbox?
MailReach recommends up to 100 emails per day per inbox for properly warmed accounts. Conservative approaches start at 30-50 per inbox.
Do I need dedicated IPs or are shared IPs fine?
Dedicated IPs give you full control over reputation. Shared pools risk contamination from other senders' behavior. We include 1-3 dedicated US-based IPs depending on plan.
What's the cost difference between flat-rate and per-inbox infrastructure?
For 50 inboxes: $129/month platform fee vs $350-420/month on Google Workspace Business Starter. For 200 inboxes: $129/month platform fee vs $1,400-1,680/month on Google Workspace.
Can I use my existing domains with Inframail?
Yes. Transfer existing domains or purchase new ones through the platform. We handle DNS configuration automatically either way.
What happens if deliverability drops across multiple clients simultaneously?
Dedicated infrastructure isolates each client's domain pool. One client's reputation issues don't contaminate others. We also provide blacklist monitoring with delisting support.
Key terms glossary
SPF (Sender Policy Framework): DNS record specifying which mail servers can send emails on your domain's behalf. Receiving servers check SPF to verify authorized senders.
DKIM (DomainKeys Identified Mail): Cryptographic signature added to emails proving authenticity. Prevents tampering between sender and recipient.
DMARC (Domain-based Message Authentication, Reporting & Conformance): Policy record telling receiving servers how to handle emails failing SPF or DKIM checks. Options include none, quarantine, or reject.
Dedicated IP: IP address assigned exclusively to your sending. Your behavior alone determines reputation. We provide 1-3 dedicated US-based IPs depending on plan.
Shared IP pool: IP addresses used by multiple senders. One user's bad behavior can affect deliverability for all users on that IP.
Email warmup: Process of gradually increasing send volume while generating positive engagement signals to build sender reputation.
Inbox placement rate: Percentage of emails landing in primary inbox vs spam or promotions folders. Proper infrastructure maintains 90%+ rates according to Supersend's research.
DNS propagation: Time required for DNS record changes to spread across global servers. Typically 24-48 hours for manual configuration.
