The 13 Best Cold Email Infrastructure Providers in 2026, Compared

How we compared

We are Winnr, so we're not neutral, and we've tried to make this list useful anyway. Every price comes from the provider's own pricing page or help center, checked in October 2026, and we say where a provider's own pages disagree with each other. We compare the cost of 50 inboxes per month, the size most teams start at, and leave out domains, because some providers include them, some charge yearly and some let you bring your own. Prices change often, so check the provider's site before you buy.

We left out sequencers such as Smartlead and lemlist that don't sell inboxes, and providers whose pricing we couldn't verify on their own site.

Two kinds of provider

• Google Workspace and Microsoft 365 inbox providers set up real Google or Microsoft accounts on your domains and hand them over, ready to connect to your sequencer. You get Google's or Microsoft's mail servers, usually at a lower price than buying the licences yourself, and the provider handles the setup. Google and Microsoft's own policies still apply to those accounts.
• SMTP mailbox providers run their own sending servers and give you SMTP/IMAP mailboxes. They are usually cheaper per inbox, are created in bulk, connect to any sequencer with an address and password, and don't depend on Google or Microsoft accounts.

Some resellers describe SMTP-only inboxes as a weakness, and SMTP providers say the opposite about Google and Microsoft. Both kinds can reach the inbox when domains are authenticated, warmed and sent at 10 to 20 cold emails per inbox per day. We cover that question in detail in SMTP vs Google Workspace vs Microsoft 365 for cold email. Many teams use both.

Comparison table at 50 inboxes

Inboxes only, before domains and add-ons, at list prices as of October 2026. Per-inbox figures in brackets are the yearly-billing equivalent.

1. Winnr: best overall value for SMTP cold email infrastructure

Winnr provides SMTP/IMAP mailboxes on its own sending infrastructure, plus the domains, DNS, warming and tooling around them. Startup is $69/month for 50 email accounts and Enterprise is $189/month for 200, with extra accounts at $1 each on either plan. See Winnr pricing.

Why it's first:

• Price. About $1.38 per mailbox at 50 and $0.95 at 200, billed monthly with no annual contract. Of the providers above, only Hypertide's Entra inboxes, Maildoso's larger packages and Inframail's flat fee at high inbox counts come in lower per inbox, and each works differently (see below).
• Setup is automatic. Buy domains inside Winnr as a one-time purchase or bring your own for free, and SPF, DKIM and DMARC are published for you (DMARC p=reject by default). Domain slots are free to raise.
• Warming and pre-warmed mailboxes in one place. Built-in warming is $0.60 per mailbox per month, and the pre-warmed marketplace sells aged domains with already-warmed mailboxes at $3 per address per month with no minimum term.
• Works with any sequencer. One-click CSV exports in the right format for 20+ tools, including Instantly, Smartlead, EmailBison, PlusVibe, ReachInbox and Salesforge.
• Built for automation. A full REST API, an MCP server and Claude Code skills, plus a universal mailbox for replies.

Consider another provider if: you want Google Workspace or Microsoft 365 inboxes (Winnr doesn't sell them), you need a dedicated IP on a small plan (Winnr's are $20/IP/month on Enterprise), or you only need a handful of inboxes.

SMTP providers on their own infrastructure

2. Mailforge

Mailforge, part of the Salesforge family, sells mailboxes on its own infrastructure using what it calls a "shared IP pool". Pricing is per mailbox "slot": $3 per slot per month on monthly billing, or $30 per slot per year, with a minimum of 10 slots. 50 mailboxes are $150/month, or $125/month billed yearly. .com domains are $14 a year, and SSL and domain masking is a $2 per domain per month add-on. It recommends 30 emails per mailbox per day and 2 to 3 mailboxes per domain, and doesn't offer a free trial. Note that the static text on its pricing page says "Billed yearly" next to the $3 price, while its calculator uses $3 for monthly billing.

Best for: teams already using Salesforge tools that want simple per-slot pricing. Compare: Winnr vs Mailforge.

3. Infraforge

Infraforge, also from Salesforge, sells "private" infrastructure on dedicated servers with dedicated IPs. Slots are $12 per quarter ($4 per month) or $40 per year, with a minimum of 10, so 50 mailboxes are $200/month billed quarterly or $166.67/month billed yearly. Additional IP addresses are $99 per IP per month, billed quarterly. API access and multi-IP provisioning are included.

Best for: senders who want dedicated IPs as the default and can commit to quarterly or yearly billing. Compare: Winnr vs Infraforge.

4. Maildoso

Maildoso sells "SMTP mailboxes" on what it describes as "fully proprietary infrastructure, including servers and IPs". Its monthly plans are fixed packages: 30 mailboxes for $75, 300 for $225 and 1,000 for $499, with custom sizes priced in the app. Domains are held by Maildoso while you subscribe and transferred to you on request. It offers an API and MCP server, recommends up to 15 cold emails per mailbox per day with 14 days of mandatory warmup, and has a 30-day money-back guarantee on monthly SMTP plans. Its own FAQ says it is optimized for B2B, with weaker placement to Gmail and Yahoo consumer addresses.

Best for: large B2B fleets that fit its package sizes (300 mailboxes for $225 is $0.75 each). Compare: Winnr vs Maildoso.

5. Mission Inbox

Mission Inbox runs its own infrastructure with dedicated servers and dedicated IPs ("No shared pools"). Its Scale plan is $199/month for 30 mailboxes, with extra mailboxes at $3, so 50 mailboxes are about $259/month. Its pages disagree on the included sending volume: the pricing page says 10,000 sends per month, while the homepage says "Unlimited sends" with a footnote of $1 per 1,000 emails. It also offers pre-warmed mailboxes, aged domains and a paid warmup add-on.

Best for: teams that want dedicated IPs on every plan and will pay more per inbox. Compare: Winnr vs Mission Inbox.

Google Workspace and Microsoft inbox providers

6. Inframail

Inframail describes its product as "Microsoft-backed inboxes" built on Microsoft's cloud platform. Pricing is a flat fee rather than per inbox: Unlimited is $147/month (or $111.47/month billed yearly), recommended for up to 400 mailboxes and including one dedicated US IP. The Agency Pack is $387/month for up to 1,000 mailboxes with 3 dedicated IPs. API access is included, connecting your own domains costs $5 per domain one time, and it recommends up to 50 sends per inbox per day.

Best for: teams that will run hundreds of inboxes, where a flat fee works out cheapest per inbox. Compare: Winnr vs Inframail.

7. Primeforge

Primeforge, the third Salesforge infrastructure brand, sells Google Workspace and Microsoft 365 mailboxes. Slots are $4.50 per month or $45 per year, with a minimum of 10, so 50 inboxes are $225/month or $187.50/month billed yearly. Domains are $14 a year, you can bring your own, and API access is included.

Best for: Salesforge users who want Google or Microsoft inboxes. Compare: Winnr vs Primeforge.

8. Zapmail

Zapmail sets up Google Workspace or Microsoft 365 inboxes, one domain per workspace. Plans combine a base fee with add-on mailboxes: on monthly billing, Starter is $39 for 10, Growth $99 for 30 and Pro $299 for 100, with extra mailboxes at $3.50, $3.25 and $3.00. 50 inboxes on Growth are $164/month, and quarterly and yearly billing are cheaper. It also sells pre-warmed plans, lists 50+ sequencer integrations, and its site states a no-refund policy.

Best for: teams that want Google Workspace inboxes set up for them, especially on longer billing terms. Compare: Winnr vs Zapmail.

9. Premium Inboxes

Premium Inboxes sells "Official Google Workspace & Microsoft 365" inboxes at the same price for both: $3.50 per inbox per month up to 249 inboxes, falling to $3.00 and $2.80 at higher volumes, or $35 per inbox per year. 50 inboxes are $175/month. There are no setup or platform fees, unlimited free replacement inboxes, API access on every plan, and it recommends 15 emails per inbox per day. An "Insured Infrastructure" tier is $4.50 per inbox.

Best for: buyers who value free replacements and month-to-month Google or Microsoft inboxes. Compare: Winnr vs Premium Inboxes.

10. Cheap Inboxes

Cheap Inboxes sells Google and Microsoft inboxes at "Same price for both": $3.50 per mailbox per month up to 99, then $3.25, $3.00 and $2.80 at higher tiers, with no setup costs or long-term contracts. 50 inboxes are $175/month. Each domain gets its own workspace with admin access, bringing your own domains is free, and it offers an API and 24/7 WhatsApp support.

Best for: teams that want Google or Microsoft inboxes with admin access to each workspace. Compare: Winnr vs Cheap Inboxes.

11. Puzzle Inbox

Puzzle Inbox sells Google Workspace inboxes at $3 each (Standard) or $4.50 (Warmed), with 3 inboxes per domain mandatory, so 50 inboxes become 51 at $153/month. It recommends 12 emails per Google inbox per day. Outlook 365 inboxes are listed at $0.35 to $0.50, sold 100 per domain at 3 emails per inbox per day, but the site currently warns "We don't recommend Outlook 365 right now". Delivery takes 24 to 72 hours, and cancellation must be requested 5 days before renewal.

Best for: teams that want Google inboxes, including a pre-warmed option. Compare: Winnr vs Puzzle Inbox.

12. Hypertide

Hypertide sells Google inboxes at $3.30 per inbox per month with "No packages, no minimums", so 50 are $165/month. It also sells Microsoft Entra domains at $25 per domain per month with 25 inboxes each ($1 per inbox), so 50 Entra inboxes are $50/month. API access, unlimited seats and 24/7 support are included, billing is month to month, and there's no free trial. Its pages give different figures for how much each Entra domain can send, so check the current limits with Hypertide before planning volume.

Best for: very low cost per inbox on Entra, or simple per-inbox Google pricing. Compare: Winnr vs Hypertide.

13. Instantly (done-for-you, pre-warmed and AirMail accounts)

Instantly is mainly a sequencer, but it also sells sending accounts inside its platform: done-for-you Google accounts at $5 per account per month, pre-warmed Google accounts at $10, and AirMail accounts, which it describes as its native email sending infrastructure, at $4. Domains are $15 a year. AirMail, announced in May 2026, is capped at 20 emails per inbox per day and is for B2B sending only. Pre-warmed accounts are sold in batches of 5, are configured for use only within Instantly, and Instantly keeps domain ownership and admin access.

Best for: teams that send only from Instantly and want everything in one bill. If you might switch sequencers, inboxes you own and can export are more flexible. Compare: Instantly email accounts vs Winnr. Smartlead sells mailboxes the same way through SmartSenders: SmartSenders vs Winnr.

How to choose

• You want the lowest cost per inbox at 50 to 200 inboxes, billed monthly, with DNS and warming handled: Winnr.
• You specifically want Google Workspace or Microsoft 365 inboxes: a reseller such as Zapmail, Premium Inboxes, Cheap Inboxes, Puzzle Inbox, Hypertide or Primeforge. Compare per-inbox price, billing term, replacement policy and whether you get admin access.
• You need to send this week: pre-warmed inboxes. Winnr's pre-warmed mailboxes are $3 per address per month with no minimum term; Zapmail, Puzzle Inbox, Mission Inbox and Instantly also sell pre-warmed options.
• You want dedicated IPs by default: Infraforge or Mission Inbox, or Winnr Enterprise with a $20/month dedicated IP.
• You'll run several hundred inboxes: compare flat-fee and large-package pricing (Inframail, Maildoso) with per-inbox pricing at your exact count.

Whichever you choose, the fundamentals decide deliverability more than the provider: authenticated domains, at least 2 weeks of warming, 10 to 20 cold emails per inbox per day, and clean lists. If you've settled on SMTP mailboxes, our comparison of the best SMTP providers for cold email goes deeper on that group. For more options, see Winnr alternatives (which also covers InboxKit and Mailpool), or read Winnr as a Google Workspace alternative.