Comparison
Feb 4, 2026
CEO and co-founder
Best Cold Email Infrastructure for Agencies: Comparison of Top Platforms 2026
What is cold email infrastructure?
Cold email infrastructure is the engine room that powers your outreach. It includes three components: domains, inboxes, and IP addresses. Your sending tools like Instantly or Smartlead connect to this infrastructure through IMAP/SMTP credentials.
Think of it this way: Instantly is the driver. Infrastructure is the car. Without proper domains configured with SPF, DKIM, and DMARC records, your emails struggle to reach the inbox. Gmail now mandates SPF, DKIM, and DMARC deployment to combat phishing and spoofing. Emails failing these checks get rejected or sent to spam based on your domain's DMARC policy settings.
The infrastructure layer handles three critical functions:
Domain registration and DNS configuration: SPF, DKIM, and DMARC records that authenticate your sending identity
Inbox provisioning: Creating email accounts with proper credentials
IP reputation management: The sending IPs that email providers use to judge your trustworthiness
Most agencies conflate sending tools with infrastructure. They're separate costs. You pay for infrastructure (domains + inboxes + IPs) and sending platforms (Instantly, Smartlead, Lemlist) independently. For a complete overview of setting up your stack, watch our Ultimate Cold Email Infrastructure Guide.
How to choose the right infrastructure for your agency
Picking infrastructure based on headline pricing is a mistake. A $2/inbox plan with shared IPs can cost you more in burned domains and lost clients than a $129/month flat-rate with dedicated infrastructure. For agencies protecting 15-20% net margins, infrastructure choices directly impact profitability. Here are the three criteria that actually matter.
True cost per inbox (TCO)
TCO includes four line items:
Platform fee: Monthly subscription cost
Domain costs: $5-$16 per domain annually
Warmup tools: $15-$50/month per inbox (if external warmup required)
Sending platform: Instantly, Smartlead, or similar ($37-$97/month)
Per-inbox models hide costs through add-ons. You see "$1.90/inbox" but miss the warmup bill for 50 accounts. Calculate your true email sending capacity before committing to any platform.
The calculation for 50 inboxes:
Google Workspace: 50 × $7-$8.40 = $350-$420/month
Inframail: $129/month flat + $68.50/month domains (amortized) = $197.50/month
Monthly savings: $152.50 - $222.50
For a $2,000/month client retainer, Google Workspace infrastructure alone consumes 17-21% of billings. Inframail drops that to roughly 8%. That difference compounds across every client you add.
Setup speed and DNS automation
Manual DNS configuration for 50 domains takes 12-15 hours for initial setup. You log into Namecheap or GoDaddy, create SPF records (v=spf1 include:spf.protection.outlook.com ~all), configure DKIM, set DMARC policies, wait 24-48 hours for propagation, then test with Mail-Tester. According to cold email setup best practices, manual DNS setup takes 15-30 minutes per domain including research, configuration, and verification.
Automated platforms handle this in seconds. One agency owner described the difference:
Watch this setup tutorial to see the actual workflow difference. That's 12-15 hours you could spend on sales calls closing $2,000-5,000/month retainers instead of configuring DNS records.
Deliverability and IP reputation
IP reputation determines inbox placement. Two types exist:
Shared IPs: Multiple senders use the same IP address. If one sender spams, everyone on that IP gets flagged. According to SendGrid's documentation, sending activity from shared IPs may be impacted by other users. Your inbox rate can drop significantly overnight because someone else broke the rules.
Dedicated IPs: You control the IP exclusively. Your sending behavior alone determines reputation. No "bad neighbors" can tank your campaigns.
Understanding the difference between dedicated and shared IPs is critical for agencies running client campaigns. When deliverability collapses, clients threaten cancellation. That monthly retainer evaporates because of infrastructure you don't control.
Support quality and response time
When deliverability crashes Friday afternoon, response time matters. With fragmented infrastructure (domain registrar, inbox provider, warmup tool, sending platform), you're troubleshooting across 3-4 vendor support teams while your client threatens cancellation.
Centralized infrastructure platforms typically offer faster resolution. Inframail provides support from 7:00 AM to 12:00 AM PST, 7 days a week according to their FAQ. Customer reviews consistently mention fast response times:
"Support is practically 24/7 with at max a 2min wait to get a question answered." - Verified user review of Inframail (Inframail now has [38 5-star reviews on Trustpilot](https://www.trustpilot.com/review/inframail.io).)
Top 5 cold email infrastructure platforms for agencies
I evaluated these platforms based on four criteria:
True cost of ownership (TCO) at 50, 100, 200 inbox tiers
IP infrastructure type (dedicated vs. shared pools)
Setup automation level (manual DNS vs. API-driven)
Support quality (response time and resolution rate)
Each platform has a specific use case where it excels.
1. Inframail
Best for: Agencies running 50-200 domains who need flat-rate pricing and dedicated IPs
Pricing model: Flat-rate unlimited
Unlimited Plan: $129/month (1 dedicated US IP, unlimited inboxes, unlimited setups)
Agency Pack: $327/month (3 dedicated US IPs, unlimited inboxes, unlimited setups)
Domains: $5-$16 each through the platform
Pros:
Flat-rate pricing regardless of inbox count
Dedicated US-based IPs (not shared pools)
Automated SPF/DKIM/DMARC configuration
Microsoft enterprise infrastructure
38 5-star Trustpilot reviews with 4.7/5 rating
Cons:
Requires external warmup tools like Warmbox ($15-50/month per inbox) or Inframail's DFY package ($299/month with free warmup included)
Microsoft-only platform (no Google Workspace option)
US-based infrastructure only
Customers consistently highlight the speed advantage:
"I can set-up inboxes in 5mins while saving money on Google Workspace subscriptions and benefit from great deliverability." - Verified user review of Inframail
The platform handles common SMTP issues automatically. For agencies managing multiple clients, the API enables bulk operations that would take hours manually.
2. Google Workspace
Best for: Small teams with fewer than 20 inboxes who need maximum deliverability
Pricing model: Per-seat
Business Starter: $7/month annual, $8.40/month flexible
Business Standard: $14/month annual, $16.80/month flexible
Pros:
Native Google deliverability (highest inbox placement)
Full productivity suite included
Established reputation with email providers
Extensive market trust and widespread adoption
Cons:
Costs scale linearly (50 inboxes = $350-$420/month)
Manual DNS configuration required
No dedicated IPs for cold email use cases
January 2025 price increase with Gemini AI bundling
At 50 inboxes, you're paying $4,200-$5,040 annually just for email infrastructure. That's before domains, warmup, or sending platforms. The real problem: add three new clients (15 more domains, ~30 inboxes) and your infrastructure bill jumps $210-252/month before you've invoiced the first retainer payment. Revenue grows in chunks. Costs grow per inbox.
3. Maildoso
Best for: Teams prioritizing quarterly billing flexibility over dedicated IPs
Pricing model: Per-inbox ($1.90-$2.75 per inbox)
Pros:
Lower per-inbox cost than Google Workspace
Quarterly billing options available
144 G2 reviews showing established user base
Premium AI warmup available as add-on (100 warmup emails per day per mailbox)
Cons:
Shared IP infrastructure with IP rotation
Per-inbox pricing still scales with volume
Warmup is an extra paid feature, not included in base plans
For 50 inboxes, Maildoso runs $95-$137.50/month. That's cheaper than Google Workspace but you're trading dedicated IP control for cost savings. With shared IP infrastructure, your deliverability may be impacted if another sender violates email marketing regulations.
4. Mailforge
Best for: Teams wanting per-mailbox flexibility with optional warmup features
Pricing model: Per-mailbox (~$3 per mailbox)
Minimum 10 mailbox slots
10 mailboxes: approximately $30/month
Pros:
Some warmup features included
4.8/5 rating on G2 with 74 reviews
Option to choose between shared and unique IP addresses
Cons:
Default shared IP pool distributes mailboxes among millions of businesses
Pricing increases as volume grows
Dedicated IP option costs significantly more
Mailforge offers flexibility in IP selection but defaults to shared infrastructure. If you choose dedicated IPs, costs increase. For agencies managing client reputation, this creates an ongoing trade-off between cost and control.
5. Mailscale
Best for: Small teams (15-50 inboxes) who want tiered pricing with built-in warmup
Pricing model: Tiered plans
Starter: $79/month (15 accounts)
Business: $119/month (50 accounts)
Scale: $327/month (200 accounts)
Pros:
Built-in deliverability tools
Predictable tier-based pricing
55 G2 reviews and 80 Trustpilot reviews
Cons:
Costs increase at volume thresholds
Jump from 50 to 200 accounts requires significant price increase
For agencies growing past 50 inboxes, the jump from $119/month to $327/month creates cost pressure. The math doesn't compound as favorably as flat-rate models when you're adding clients incrementally.
Comparison: Flat-rate vs. per-inbox pricing models
The difference between pricing models becomes stark at scale. Here's the math across three volume tiers.
Provider | 50 Inboxes/Month | 100 Inboxes/Month | 200 Inboxes/Month | IP Type | % of $2K Retainer* |
|---|---|---|---|---|---|
Inframail | $163** | $163** | $163** | Dedicated | 8.2% |
Google Workspace | $350-$420 | $700-$840 | $1,400-$1,680 | N/A | 17.5-21% |
Maildoso | $95-$138 | $190-$275 | $380-$550 | Shared | 4.8-6.9% |
Mailforge | ~$150 | ~$300 | ~$600 | Shared | 7.5% |
Mailscale | $119 | $119 | $249 | Varies | 6% |
Based on 50 inbox tier only, calculated as (Infrastructure Cost ÷ $2,000 Client Retainer)
*Inframail pricing includes $129/month platform + ~$34/month amortized domain costs
Annual savings with Inframail vs. Google Workspace:
50 inboxes: $2,244-$3,084/year
100 inboxes: $6,444-$8,124/year
200 inboxes: $14,844-$18,204/year
The real insight: per-inbox costs grow faster than revenue. Adding three clients doesn't triple your billings, but Google Workspace triples your infrastructure bill. One reviewer captured the unit economics impact:
"So affordable that it will make your unit economics work, even for lower ticket b2b businesses like ours." - Verified user review of Inframail
Why dedicated IPs matter for agency scaling
Shared IP pools work like carpool lanes. Your email reputation depends on everyone in the lane. One bad actor spamming gets the entire IP range flagged. Your carefully warmed-up inboxes suddenly hit lower inbox rates because someone else sent spam.
Dedicated IPs work like private lanes. Your sending behavior alone determines ESP trust. You control warmup pacing, volume ramps, and content quality. If deliverability drops, you diagnose your own campaigns rather than waiting for unknown senders to stop spamming.
The practical difference shows up in blacklist scenarios. With shared IPs, you wake up to Spamhaus listings you didn't cause. With dedicated IPs, Inframail's monitoring tracks blacklists and auto-submits delisting requests when domains get flagged.
When inbox rates drop from 80% to 50%, meeting volume collapses. Your client who expects 8-10 meetings monthly suddenly gets 3-4. That's when the cancellation email arrives and you lose monthly recurring revenue because of infrastructure you don't control.
Learn how to tell if your campaign emails are going to spam and what healthy metrics look like for each IP type.
Making the switch: What to expect
Migrating infrastructure requires planning. Here's the realistic timeline:
Day 1-3: Set up new domains and inboxes on new platform
Day 4-18: Warm up inboxes to establish sending reputation
Day 19-30: Run parallel campaigns on old and new infrastructure
Day 31+: Fully migrate and decommission old accounts
Month-to-month flexibility at Inframail enables testing without annual contracts.
Common migration gotchas to avoid
Most agencies hit three problems during migration:
Rushing warmup: They launch campaigns on day 5 instead of day 18, tanking deliverability before it's established.
No parallel testing: They fail to run parallel campaigns for validation, discovering deliverability issues only after decommissioning old infrastructure.
All-at-once migration: They migrate all clients simultaneously instead of piloting with 1-2 non-critical accounts first.
The safe approach: Migrate your lowest-value client first. Run 500-1,000 sends over 14 days. Track inbox placement with spam testing tools. If metrics match or exceed your Google Workspace baseline (75-85% inbox rate), migrate the next client. If you're below 70%, pause and troubleshoot before committing more domains.
Budget 45-60 days for complete migration if you're moving 50+ domains. One week per 10-15 client domains is realistic when you account for warmup, testing, and validation cycles. Time to first campaign live drops from 7-10 days (manual DNS) to same-day when DNS auto-configures.
"We spent months hunting for a reliable cold-emailing stack. After repeated failures with another provider, we trialled two options... A month later, we switched back to Inframail. Zero issues since. Rock-solid infrastructure." - Verified user review of Inframail
Inframail's YouTube channel features user interviews showing real results from agencies using the platform. One interview covers closing a $50,000 client through cold email outreach.
Ready to cut your infrastructure costs?
The math is clear: for agencies running 50+ domains, flat-rate dedicated IP infrastructure saves $152.50 - $222.50/month compared to Google Workspace. That's $2,244-$3,084 annually. Enough to fund a junior account manager or add 10-12% to your net margin.
Sign up for Inframail and get started today. Test with 10-20 domains for your first month. Run the numbers on your actual campaigns. Calculate your infrastructure cost as % of billings before and after. The savings compound faster than the switching cost.
Frequently asked questions
Do I need to warm up Inframail inboxes?
Yes. Use external warmup tools like Warmbox or Instantly's warmup feature. Budget $15-$50/month per inbox or use Inframail's DFY package ($299/month) which includes free warmup.
Can I use these inboxes for regular business email?
No. Cold email infrastructure is optimized for outreach volume. Use Google Workspace or Microsoft 365 for internal company communication.
How fast is the actual setup process?
Domain to live inbox takes under 5 minutes with Inframail's automation. Manual DNS configuration takes 15-30 minutes per domain. For 50 domains, that's 12-15 hours manual vs. under 2 hours automated.
What happens if my IP gets blacklisted?
Inframail monitors blacklists and auto-submits delisting requests. With dedicated IPs, you only get listed for your own behavior, not someone else's spam campaigns.
Does Inframail work with Instantly and Smartlead?
Yes. Export IMAP/SMTP credentials to CSV and import directly into any major sending platform.
How do I calculate my current infrastructure cost as % of billings?
Total your monthly costs: (Domains + Inboxes + Warmup + Sending Platform). Divide by total monthly client revenue. Example: $680 infrastructure ÷ $8,000 billings = 8.5%. Target 15-18% maximum. Above 25% signals unit economics problems requiring pricing increase or infrastructure switch.
What happens when deliverability crashes on Friday afternoon?
Inframail support operates from 7:00 AM to 12:00 AM PST, 7 days a week. Most issues resolve in one diagnostic conversation. With fragmented infrastructure, you're troubleshooting across 3-4 vendor support teams while your client threatens cancellation.
Key terminology
SPF (Sender Policy Framework): A DNS record listing approved mail servers that can send email on behalf of your domain. Without it, emails fail authentication.
DKIM (DomainKeys Identified Mail): A digital signature proving your email is authentic and hasn't been tampered with during transit.
DMARC (Domain-based Message Authentication, Reporting & Conformance): Instructions telling email receivers what to do with emails that fail SPF or DKIM checks. Options include none, quarantine, or reject.
Dedicated IP: An IP address assigned exclusively to your sending. You control your own reputation completely without influence from other senders.
Shared IP: An IP address used by multiple senders simultaneously. Your email deliverability depends partly on other senders' behavior on that IP.
Infrastructure cost as % of billings: Total monthly infrastructure spend (domains + inboxes + warmup + sending platform) divided by total client revenue. Healthy agencies maintain 15-18% or less. Above 25% indicates margin squeeze requiring pricing increase or infrastructure switch.
