MailDeck is a cold email infrastructure provider managing 833.9K+ inboxes for 1,631+ clients across three platforms: Microsoft 365 Outlook, Google Workspace, and Private SMTP. Most competitors specialize in one infrastructure type. MailDeck covers all three so teams can match their infrastructure to their target audience. Based on Q1 2026 platform data.

What is cold email infrastructure?

Cold email infrastructure is the technical setup required to send high-volume outreach emails reliably. It includes dedicated sending domains, mailboxes, DNS authentication (SPF, DKIM, DMARC), IP warmup, and ongoing deliverability monitoring. The choice of infrastructure (Microsoft 365 Outlook, Google Workspace, or SMTP) determines roughly 60% of deliverability. Domain health, copy quality, and list quality determine the rest.

What infrastructure types does MailDeck support?

MailDeck supports three infrastructure types under one provider: Microsoft 365 Outlook (Azure tenants with dedicated US IPs, 100 inboxes per tenant), Google Workspace (real Starter accounts on Google's official IP pools, 5 inboxes per domain), and Private SMTP (dedicated IP per client, 5 inboxes per domain). All three are equally supported.

How much does MailDeck cost?

Microsoft 365 Outlook tenants start at $30 per tenant for the Normal Licence ($0.30 per inbox, 100 inboxes per tenant). Premium Licence is $40 per tenant ($0.40 per inbox). Mixed Licence (50 Normal + 50 Premium per tenant) is $35 per tenant. Pre-Warmed Outlook inboxes are $50 per tenant. Google Workspace plans start at $39 per month for 10 inboxes ($3.90 per inbox), with Growth at $99 per month for 30 inboxes and Enterprise at $299 per month for 100 inboxes. Private SMTP is $0.50 per inbox with a 100-inbox minimum ($50/month). Diversified Stack plans combining all three start at $99 per month.

Which MailDeck product has the best deliverability?

Google Workspace inboxes deliver the highest inbox placement because they use Google's official IP pools, which carry the highest trust score across receiving servers worldwide. Microsoft 365 Outlook is second, also using bulletproof official Microsoft IP pools. Private SMTP is fourth because reputation is built from scratch per client. Across the entire MailDeck platform, average inbox placement holds at 98%.

How quickly are MailDeck inboxes provisioned?

Provisioning times differ by product. Google Workspace inboxes are provisioned instantly. Private SMTP inboxes are delivered within 24 hours. Microsoft 365 Outlook inboxes take 2-3 business days because Azure tenant provisioning involves Microsoft-side setup. All three products include full SPF, DKIM, and DMARC configuration plus end-to-end DNS verification before the first email is sent.

How many cold emails can I send per inbox per day?

Microsoft 365 Outlook Normal Licence supports 3-5 cold emails per inbox per day. Microsoft 365 Outlook Premium Licence supports 8-10. Google Workspace supports 18-22. Private SMTP supports 11-14. These limits are based on Q1 2026 MailDeck platform data and are tuned to maintain inbox placement above 95% across receiving servers.

How many inboxes do I need for cold email?

Inbox count depends on monthly send volume and infrastructure mix. For 100K emails per month using a Diversified Stack at the recommended 50/30/20 ratio, roughly 16 domains are needed: 3 Microsoft 365 Outlook tenants (300 inboxes), 6 Private SMTP domains (30 inboxes), and 7 Google Workspace domains (33 inboxes). For higher volumes the math scales linearly. A 1M sends per month operation typically requires 150-200 active domains plus a 20-25% warm reserve.

How long does cold email warm-up take?

Microsoft 365 Outlook Premium Licence requires 3-5 days minimum, ideally 10-14 days. Microsoft 365 Outlook Normal Licence requires 5-7 days minimum, ideally 10-14 days. Google Workspace requires 15 days minimum, ideally 20-25 days. Private SMTP requires 3-4 weeks minimum and 6+ weeks for high-volume use. MailDeck Pre-Warmed Outlook inboxes at $50 per tenant skip warmup entirely and are ready for cold sending immediately.

Does MailDeck use shared IPs?

No. MailDeck never uses shared IPs. Microsoft 365 Outlook inboxes use official Microsoft IP pools, which are whitelisted across virtually every receiving server. Google Workspace inboxes use official Google IP pools, which carry the highest trust score on the internet. Private SMTP uses dedicated IPs per client where reputation is built from scratch and is never shared with other senders.

Does MailDeck handle DNS authentication?

Yes. MailDeck automates SPF, DKIM, and DMARC setup for every domain. DNS propagation and end-to-end authentication are verified before the first email is sent. A MailDeck DNS audit of 1,000+ domains found that 67% had at least one critical authentication error. The most common errors were multiple SPF records on one domain (23%), missing DMARC record (19%), and SPF ending with +all (14%).

Does MailDeck work with Instantly, Smartlead, and other sequencers?

Yes. All MailDeck inboxes connect via SMTP to every major sequencer including Instantly, Smartlead, Saleshandy, Apollo, Lemlist, Woodpecker, Reply.io, Snov.io, QuickMail, GMass, Klenty, Mailshake, and any SMTP-compatible outreach tool. The sequencer is a scheduler and does not affect deliverability. Inbox type, domain health, copy quality, and list quality determine deliverability.

Do I need to bring my own domains?

Yes. Clients bring their own domains. MailDeck handles full DNS configuration, SPF, DKIM, and DMARC setup, and propagation verification on the domains the client provides during onboarding.

How does MailDeck compare to Maildoso, Infraforge, and Mailforge?

MailDeck Microsoft 365 Outlook inboxes start at $0.30 per inbox on official Microsoft IP pools. Maildoso uses shared IP pools at approximately $2.50 per inbox, carrying shared IP risk where one bad sender hurts all clients. Infraforge is Microsoft-only at approximately $4.00 per inbox without official Microsoft IPs. Mailforge uses shared IP SMTP at approximately $3.00 per inbox with shared IP risk. MailDeck is the only provider in the niche offering Microsoft 365, Google Workspace, and SMTP under one platform with zero shared IP exposure.

What happens if a domain gets burned?

MailDeck includes free domain replacement when a domain burns under normal sending conditions. At enterprise scale (100K+ emails per month) approximately 10-20% of cold email domains burn monthly with domain lifespan ranging 45 days to 2 months under active load. MailDeck recommends maintaining a 20-25% warm reserve so replacement happens within 1-3 days without breaking campaign cadence. Without reserves, replacement takes 7-10 days.

What cold email copy rules should I follow?

Copy rules differ significantly by provider. Google Workspace inboxes are the most permissive: links, open tracking, and ESP matching (Google-to-Google) are safe to use, and images in signatures are acceptable. Microsoft 365 Outlook (both Normal and Premium) requires strict rules: no links in body copy because the Safe Links scanner triggers, no open tracking because Outlook checks messages before delivery and tracking pixels spike spam detection, no ESP matching, no dollar signs or financial language, maximum 50 words per email, and spintax on every 2-3 words. Private SMTP should never be used as the primary sending protocol and is best capped at 30% of total send volume to absorb spikes and protect premium inboxes. These rules are derived from data on 270M+ cold emails sent through the MailDeck platform.

MailDeck serves the full range of cold email senders. 1,631+ clients across Q1 2026 platform data include solopreneurs running their own outbound at 30K-50K emails per month, small teams scaling from 50K to 100K, growing leadgen and outbound agencies managing 100K-300K emails per month across multiple clients, B2B sales teams targeting enterprise accounts, SaaS companies selling into mid-market and enterprise, and enterprise operations sending 1M+ per month. Platform sends 7.5M+ emails per day and has delivered 270M+ cold emails lifetime.

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Trusted by the highest sender cold email teams sending millions monthly.
Built by cold emailers for cold emailers with scaleability and deliverability as primary focus.
Fully managed. 24/7 deliverability audit.

833.9K+

Inboxes Managed

7.5M+

Emails / Day

1631+

Global Clients

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4.8

Google

4.9

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*Estimated. The results depend on several factors including offer quality and sending volume.

Infrastructure Standard

Why Industry Leaders Choose MailDeck?

"Cold email infrastructure across Microsoft 365, Google Workspace, and SMTP. Fully configured, fully managed, ready in 48-72 hours."

Microsoft 365, Google Workspace, and SMTP under one provider

Official Microsoft and Google IPs, never shared pools

Full "turnkey" setup in 48-72 hours

Loaded into your sending program automatically

Warm-up included, ready to send from day one

Free domain replacement on burn

24/7 priority support

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The Proof Layer

Trusted by
High-Volume Teams.

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Join +950 Experts

Mike Wentworth

Director of Outbound | HR Tech Solutions

12k leads reached. 1,697 unique replies. 831 positive responses. that's a +5% reply rate and +45% of replies were interested. we've been running this for a quarter now and our domains are still healthy. Sabo and his team really set our infrastructure up like its their own.

Tommy Vaughn

Marketing Agency (EdTech Niche)

Small team, needed big results. Under 10k emails out, +500 replies, more than 200 interested of MailDeck helped us punch way above our weight class without needing a huge SDR team.

David N.

Fintech Agency Owner

REACHED 1297 LEADS and 149 REPLIED and 31 SHOWED REAL INTEREST. We were skeptical about cold email after getting burned by a previous vendor who destroyed dozens of our domains, but Maildeck's 20.8% positive reply rate proved us wrong. Their warmup system actually works.

Mike Chen

b2b saas growth partner

we used to obsess over opens. with maildeck we mostly watch replies, bounces and how many calls land on the calendar. around 180–200k sends a month, 3-5% replies HUMAN!, nothing crazy. but it’s stable, and their infra guys ping us before things break, not after.

Marcus L.

Founder, AdGravity Ecom

We blew up hundreds of domains last year sending pretty HTML newsletters as ‘cold outreach’. Maildeck made us strip everything back to 1–2 line, plain‑text notes and 3-5 cold emails per inbox per day. Felt underpowered at first, until we realized we were actually booking more discovery calls from half the volume.

Michael Walter.

Co‑Founder, SentinelSec Cyber

Cyber clients are allergic to spammy tools, so we were cautious. Maildeck started us with slow warmup, rigid verification, and zero tracking or links. We hover around 6% reply rate on 10–12k sends/month, but the important part is we haven’t had a single tenant locked or reputation fire drill since switching.

Jake Rodriguez

Founder @ Real Estate Agency

We tested three sequences - 81k, 42k, and 62k emails. The middle campaign crushed it: 11% reply rate, +45% positive responses. Maildeck's team helped us dial in the messaging for each segment. No more spray and pray.

Jenna M.

SignalStack Data Studio

Data enrichment agency here. Honestly thought tools didn’t matter, only lists. Turns out infra + rules matter a lot when Outlook is watching everything. We send around 500k cold emails over multiple tenants got around 5% reply rates +40% positive replies, $300k/mo in the pipeline in first two months bounce under 1.5%.

Alex G.

Director, NovaChannel Outbound Collective

We manage outbound for a mix of agencies, consultants and SaaS founders. Maildeck’s whole ‘TAM + angle first, then scale’ thing forced us to stop guessing. Now we stagger tests, track repl to positive to call for each angle, and only ramp what proves itself. We sit a bit above 850k sends/month, but it never feels reckless because each inbox is throttled and watched.

Chen Wei

B2B Consulting - Healthcare IT

Started small to test the waters (50k emails). Got 147 positive replies Gave us confidence to scale up to our big 200k campaign next, can’t wait to go even higher. Sabo's team really understands gradual scaling.

ALEX KOWALSKI

Head of Growth, FinTech Company

163,085 emails. 10,981 replies. 4,742 interested prospects. those are the numbers from our last 10 days. the reply rate sits at 6.73% which might not sound huge but when you're doing volume like this it's a FLOOD of conversations. bounce rate stayed at 1.31% the whole time. maildeck's infrastructure is legit.

Steven Grant

Co-Founder, AI Automation Agency

Two months, 246,263 emails sent, 2,479 replies (5.38% rate), 1,280 marked as interested (51.64% of replies were positive). Only 2569 bounces across the entire 60-day period. This is sustainable outbound - not the burn-and-churn approach we dealt with before.

Mike Wentworth

Director of Outbound | HR Tech Solutions

Tommy Vaughn

Marketing Agency (EdTech Niche)

Small team, needed big results. Under 10k emails out, +500 replies, more than 200 interested of MailDeck helped us punch way above our weight class without needing a huge SDR team.

David N.

Fintech Agency Owner

Mike Chen

b2b saas growth partner

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Ask Maya anything about the cold email stack — infrastructure, lists, personalization, replies. She explains how the system works.

Internal Schematic 0.94-B

Deliverability Architecture.

We don't hope for the primary inbox. We engineer the path to it using a four-layer verification stack.

Enterprise Isolation Protocol

Our proprietary system ensures that if one inbox is flagged, the entire fleet remains undetected.

99.8%

Placement

0ms

Latency

Efficiency Audit

You Are Drastically Undersending.

Visibility is the Issue, Not Your Website or Offer. Not enough people are seeing your outreach. Imagine how many more meetings you would book with 20x more outreach for the same money.

01. Limited TAM?

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02. Scaling Costs Too Much?

20x Cost Reduction

You are being overcharged by Microsoft and resellers by upto 20x, that ends here.

03. Complex Setup Process?

Automated Hardening

Setting up DNS records, DKIM, SPF, and DMARC for each account is time-consuming and technical. We handle it all.

Expenses

Cost Comparison

(1,000 Inboxes)

Google / Outlook / Others

7,500$/mo

MailDeck

550$/mo

COMPETITIVE ANALYSIS

Platform Benchmarking.

A technical deep-dive into how MailDeck infrastructure stacks up against traditional methods.

Deliverability

Private SMTP

Poor From Start

Standard Resellers

Burnt in 1-2 Weeks

Microsoft Directly

Highest

MailDeck

Highest

User IP

Private SMTP

Varies

Standard Resellers

Asia

Microsoft Directly

Varies

MailDeck

US/EU only

Pricing per Inbox

Private SMTP

$3-4/month

Standard Resellers

$1-2/month

Microsoft Directly

$7.5/month

MailDeck

$0.45/month

Tool Integration

Private SMTP

Limited or manual

Standard Resellers

Limited

Microsoft Directly

Limited

MailDeck

Seamless tools

Support Quality

Private SMTP

Minimal support

Standard Resellers

Limited avail.

Microsoft Directly

Standard hours

MailDeck

24/7 support

Email Setup

Private SMTP

Manual setup

Standard Resellers

Not included

Microsoft Directly

Not included

MailDeck

Included

DNS Config

Private SMTP

Not configured

Standard Resellers

Configured

Microsoft Directly

Not configured

MailDeck

Complete DNS

Features	Private SMTP	Standard Resellers	Microsoft Directly	MailDeck
Deliverability	Poor From Start	Burnt in 1-2 Weeks	Highest	Highest
User IP	Varies	Asia	Varies	US/EU only
Pricing per Inbox	$3-4/month	$1-2/month	$7.5/month	$0.45/month
Tool Integration	Limited or manual	Limited	Limited	Seamless tools
Support Quality	Minimal support	Limited avail.	Standard hours	24/7 support
Email Setup	Manual setup	Not included	Not included	Included
DNS Config	Not configured	Configured	Not configured	Complete DNS

* Comparison based on Q4 2024 active performance data

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Normal License

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$30/month per domain

100 Inboxes / Domain

4-5 cold emails safely per inbox/day

500+ emails / day sending volume / domain

Complete Technical Setup

Free Domain Replacement

Individual US Microsoft Tenants

+15 Sending Tool Integration

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Before You Purchase

Don't leave your pipeline exposed. We recommend keeping 50% of your capacity as a warm reserve, always ready to absorb a full provider outage.

Follow the golden backup ratio: 50% Outlook for high-trust bulk, 30% SMTP for cheap volume, and 20% Google for highest deliverability.

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Why Industry Leaders Choose MailDeck?

Trusted by High-Volume Teams.

Meet Maya.Your guide through the cold email stack.

Deliverability Architecture.

You Are Drastically Undersending.

Platform Benchmarking.

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Scaling Room

Cold Email Infrastructure Cost: 2026 Pricing Comparison Across 11 Providers

Cold Email Domain Rotation: When and How to Rotate Sending Domains

Cold Email Deliverability Checklist: 15-Point Audit Template

Cold Email Warm Up: What Actually Works in 2026

Cold Email ROI Calculator: Revenue and Cost Per Lead

Cold Email Infrastructure Diversification: Why One Provider Isn't Enough

How Many Inboxes Do You Actually Need? Data from 500+ Cold Email Campaigns

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From Blank Grids to Saturated Pipelines.

JUNE / 2026

Why Industry Leaders Choose MailDeck?

Trusted by High-Volume Teams.

Meet Maya.Your guide through the cold email stack.

Deliverability Architecture.

You Are Drastically Undersending.

Platform Benchmarking.

Choose Your Foundation.

Scaling Room

Cold Email Infrastructure Cost: 2026 Pricing Comparison Across 11 Providers

Cold Email Domain Rotation: When and How to Rotate Sending Domains

Cold Email Deliverability Checklist: 15-Point Audit Template

Cold Email Warm Up: What Actually Works in 2026

Cold Email ROI Calculator: Revenue and Cost Per Lead

Cold Email Infrastructure Diversification: Why One Provider Isn't Enough

How Many Inboxes Do You Actually Need? Data from 500+ Cold Email Campaigns

Got Questions?

From Blank Grids to
Saturated Pipelines.

Trusted by
High-Volume Teams.

Meet Maya.
Your guide through the cold email stack.

Stay Ahead of
the Competition.

From Blank Grids to
Saturated Pipelines.

Trusted by
High-Volume Teams.

Meet Maya.
Your guide through the cold email stack.