One question comes up a lot when people start scaling cold email: "Where should I build my email infrastructure?"
There are plenty of cold email infra providers to choose from, and it can be hard to see what really sets them apart.
The differences usually come down to the infrastructure they provide, what you get for your money, and how much control you have over your setup.
I wanted to understand these differences better, so I compared 15+ cold email infrastructure providers myself and shortlisted the 8 best-performing ones.
I looked at their mailbox and domain options, IP infrastructure, pricing, warmup features, integrations, and scaling capabilities.
Plus, I also researched customer reviews to see what users liked, what caused problems, and what their experience was after signing up.
Here's what I found.
Check this table for a quick overview of the top cold email infra providers and what a full cold email infrastructure setup looks like with each one.
| Mailforge | Primeforge | Infraforge | Maildoso | InboxKit | Zapmail | Inframail | Mailscale | |
|---|---|---|---|---|---|---|---|---|
| Best for | Agencies and GTM teams running cold outreach at scale | Outbound teams and agencies that want provider mailboxes | Sales teams & agencies that need private infrastructure | GTM teams that want SMTP mailboxes | Outbound teams that need Google, Microsoft, or Azure mailboxes | Outreach teams that want managed provider mailboxes | Agencies managing a large number of inboxes | Small teams with no technical resource |
| Infrastructure model | Shared | Google Workspace and Microsoft 365 | Private with dedicated IPs | Shared, SMTP | Google Workspace, Microsoft 365, Azure | Google Workspace and Microsoft 365 | Dedicated | Managed |
| Mailbox type | Shared IP mailboxes | Google Workspace and Microsoft 365 | Mailboxes on dedicated IPs | SMTP | Google Workspace, Microsoft 365, Azure | Google Workspace and Microsoft 365 | Dedicated US IP infrastructure, Google and Microsoft added separately | Managed email accounts |
| Starting price | From $3 per mailbox slot per month, annual | From $4.50 per mailbox per month | From $33 per month for 10 slots, annual | From $75 per month for 30 mailboxes | From $3 per mailbox per month | From $39 per month for 10 mailboxes | $147 per month, Unlimited Plan | $79 per month for up to 15 accounts |
| Domains | Pay separately | Pay separately | Pay separately | $12 per year on monthly plans | Pay separately | Pay separately | Pay separately | Pay separately |
| Free domain connections | Yes, transfer in with no transfer fee | Yes, connect or transfer with no fee | Yes, free domain transfers | Yes, connect domains you already own | Not listed | Not listed | Yes, connect domains you already own | Not listed |
| Pre-warmed mailboxes | Yes | Yes | Yes | N/A | Yes | Yes | Not listed | Yes |
| Dedicated IPs | No | Runs on Google and Microsoft IPs | Yes, $99 per IP per month, billed quarterly | No, IP rotation instead | No, provider IPs | No, provider IPs | Yes, 1 on Unlimited, 3 on Agency Pack | Not listed |
| Workspaces | Yes | Yes | Yes | Mailbox isolation | Yes | Not listed | Not listed | Not listed |
| API, MCP, CLI | All three | All three | All three | API and MCP | API and webhooks | API access | API access | Not listed |
Mailforge is a shared cold email infrastructure platform for cold outreach. It gives teams one place to handle domain and mailbox management, DNS configuration, and sending infrastructure.
Instead of running your own email servers, you can use Mailforge's shared IP infrastructure for outbound sending. Mailforge handles the technical setup for domains, mailbox provisioning, authentication setup, and hosting.
Another useful part is the bulk management. Mailforge lets you update DNS records, organize accounts across workspaces, and manage domains and mailboxes at scale. You can also use pre-warmed domains and mailboxes for outbound campaigns.
The best part is the flexibility around domains and infrastructure management. You can transfer existing domains to Mailforge without paying a domain transfer fee.
Bonus point: Mailforge offers API, MCP, and CLI access to make it easy for technical teams to manage their infrastructure.
Mailforge starts at $3 per mailbox slot per month on annual billing. The minimum purchase is 10 slots, while domains cost extra.
Mailforge has 80+ reviews on G2. Users often mention its ease of use, quick setup, affordability, scalability, and time savings. Reviews also highlight bulk domain and mailbox management, automated DNS setup, and the ability to keep outbound infrastructure in one place.
Mailforge is best for agencies, GTM teams, and all types of businesses that need multiple domains and mailboxes for cold email without managing their own email servers.
The platform also makes sense for teams sending at scale that want to keep infrastructure costs lower while increasing mailbox volume.
Primeforge provides Google Workspace and Microsoft 365 mailboxes for cold outreach. It gives teams one place to provision and manage business mailboxes for outbound campaigns.
Instead of using shared SMTP infrastructure, you can use Google or Microsoft mailboxes through Primeforge. The platform handles mailbox provisioning, domain configuration, authentication, and other setup tasks.
Another useful part is provider matching. Primeforge lets you choose Google Workspace or Microsoft 365 based on your campaign requirements. Pre-warmed mailboxes also give you an option to start with accounts prepared for outbound use.
The best part is the flexibility around domains and account management. You can connect existing domains or transfer them without a transfer fee. API, MCP, and CLI access also give teams more ways to manage their infrastructure.
Primeforge starts at $4.50 per mailbox per month, with volume pricing going down to around $3.50 per mailbox. A minimum of 10 mailbox slots applies, and domains cost extra.
Primeforge has 10+ reviews on G2. Users commonly mention easy setup, quick provisioning, simple domain management, deliverability, and responsive support. Some reviewers also mention the time saved by having Google and Microsoft mailboxes prepared instead of setting them up manually.
Primeforge is useful for sales teams, RevOps teams, agencies, and GTM teams that want Google Workspace or Microsoft 365 mailboxes for outbound campaigns.
It also works well for teams running multiple campaigns that need different email providers for their sending accounts.
Next on my list is Infraforge. It provides private email infrastructure with dedicated IPs for outbound campaigns. Infraforge lets you manage domains, mailboxes, IPs, and sending infrastructure from one platform.
Instead of using shared IP infrastructure, you can keep your sending environment separate with dedicated IPs and build a strong sender reputation. Infraforge handles domain configuration, authentication, mailbox provisioning, and other infrastructure tasks.
Another useful part is the control over multiple sending environments. You can manage separate infrastructure for different campaigns or clients. Pre-warmed infrastructure, sender rotation, and sending limits also help when mailbox volume increases.
The best part is the range of management options. Infraforge provides API, MCP, and CLI access for technical workflows. Agencies can also use white-label options when managing infrastructure for clients.
Infraforge starts at $33 per month for 10 mailbox slots on annual billing. Dedicated IPs cost $99 per month per IP, billed quarterly.
Infraforge has 50+ reviews on G2. Users often mention easy setup, automation, speed, and reduced manual infrastructure work. Reviews also highlight the ability to manage infrastructure from one platform.
Infraforge is useful for agencies and outbound teams that want private infrastructure with dedicated IPs instead of shared sending infrastructure.
It also works well for teams managing multiple clients or campaigns that need separate sending environments.
Maildoso provides SMTP mailboxes and domain infrastructure for cold email. It gives teams one place to provision and manage large numbers of sending accounts.
Instead of handling each mailbox and domain manually, you can use Maildoso to automate much of the setup. The platform also uses IP rotation, self-healing mailboxes, and domain protection to manage the infrastructure.
Another useful part is the volume pricing. Maildoso lowers the per-mailbox cost as you increase mailbox volume. You can also connect domains you already own or purchase domains through the platform.
The best part is the automation support. API and MCP access let teams manage domains and mailboxes programmatically. Free deliverability audits and mailbox monitoring add more visibility into cold email deliverability.
Maildoso starts at $75 per month for 30 SMTP mailboxes. Larger plans include 300 mailboxes for $225 per month and 1,000 mailboxes for $499 per month. Domains cost $12 per year on monthly plans.
If you're unsure about Maildoso or want to compare more options, check out these Maildoso alternatives.
Maildoso has 180+ reviews on G2. Users frequently mention affordability, easy setup, quick provisioning, customer support, and managing large mailbox volumes. Reviews also highlight automated DNS, mailbox isolation, and deliverability as useful parts of the platform.
Maildoso is useful for agencies and teams that manage a large number of mailboxes for cold outbound campaigns.
It also makes sense for high volume outreach where keeping the cost per mailbox low matters as mailbox volume increases.
InboxKit provides Google Workspace, Microsoft 365, and Azure mailboxes for outbound email. It gives teams one place to manage mailbox provisioning, DNS, monitoring, and integrations.
You can choose Google or Microsoft mailboxes based on your campaign requirements. InboxKit also supports Azure enterprise mailboxes, while automated SPF, DKIM, and DMARC setup handles the main authentication records.
Another useful part is the integration support. InboxKit connects with 16+ sequencers according to its G2 pricing listing, while its own materials promote 24+ integrations. Real-time DNS monitoring and deliverability monitoring also give teams more visibility into mailbox health.
The best part is the choice of email providers. You can manage Google Workspace, Microsoft 365, and Azure infrastructure from one platform. API access, webhooks, 2FA, and app passwords add more control over mailbox management.
InboxKit pricing starts at $3 per Google Workspace or Microsoft 365 mailbox per month. Azure Enterprise mailboxes start at $30 per domain for up to 100 mailboxes.
If you're unsure about InboxKit or want to compare more options, check out these InboxKit alternatives.
InboxKit has 10+ reviews on G2. Users mention affordable pricing, fast setup, automation, clean UI, and the ability to manage Google, Microsoft, and Azure mailboxes from one place. Several reviews also highlight the time saved through automated DNS and mailbox provisioning.
InboxKit is useful if you want Google Workspace or Microsoft 365 mailboxes without managing every account manually.
It also works well when inbox placement, mailbox monitoring, integrations, and multiple provider options matter.
Zapmail provides Google Workspace and Microsoft 365 mailboxes for cold outreach. It handles mailbox provisioning, domain setup, and account management from one platform.
You can choose Google or Microsoft accounts based on the campaign you want to run. Zapmail also offers pre-warmed mailboxes, so you can start with accounts that have already gone through the initial preparation process.
Another useful part is the deliverability tooling. Zapmail provides deliverability tests and AI insights that give you more information about inbox placement rates before increasing sending volume.
The best part is the managed setup. You can provision multiple mailboxes without handling account creation and configuration yourself. Just keep in mind that mailbox pricing moves to standard renewal rates after the first 12 months.
Zapmail starts at $39 per month for 10 mailboxes. Standard renewal pricing increases after the first 12 months, so check the renewal cost before choosing a long-term plan.
If you're unsure about Zapmail or want to compare more options, check out these Zapmail alternatives.
Zapmail has 5+ reviews on G2, so the independent review sample remains small. Users who have reviewed the platform mention easy setup, simple infrastructure management, and responsive customer support.
Zapmail is useful for teams that want Google Workspace or Microsoft 365 mailboxes with a managed setup.
It also works well when a plan-based model is easier to manage than setting up every mailbox manually.
Inframail provides dedicated email infrastructure with unlimited inboxes. It gives teams a fixed infrastructure plan instead of charging separately for every inbox.
Each main plan includes automated DNS setup and dedicated US IP infrastructure. The Unlimited Plan includes one dedicated IP, while the Agency Pack includes three dedicated US IPs.
Another useful part is the unlimited inbox model. You get unlimited email accounts without paying an extra fee for every mailbox. Inframail also lets you buy domains through the platform or connect domains you already own.
The best part is the flat-rate structure for larger operations. API access, automated domain setup, dedicated IPs, and deliverability support come with the infrastructure plans. That makes the monthly cost easier to calculate when mailbox volume grows.
The Unlimited Plan costs $147 per month and includes unlimited inboxes and one dedicated US IP. The Agency Pack costs $387 per month and includes three dedicated US IPs.
If you're unsure about Inframail or want to compare more options, check out these Inframail alternatives.
Inframail has 30+ reviews on Trustpilot and a 4.5/5 TrustScore at the time of writing. Users frequently mention fast setup, responsive support, ease of use, and the convenience of managing large numbers of inboxes.
Read Inframail reviews on Trustpilot
Inframail is useful for agencies and teams managing a large number of inboxes for email outreach.
The flat-rate model becomes more relevant when your outreach efforts are large enough to justify a fixed infrastructure cost.
Mailscale provides managed email infrastructure for outbound campaigns. It gives teams a way to manage multiple email accounts without running their own email servers.
You can choose a plan based on the number of email accounts you need. The Solopreneur plan supports up to 15 accounts, while Business/Agency and Enterprise plans increase that capacity.
Another useful part is the managed infrastructure. Mailscale handles the technical setup behind the accounts, so teams do not have to maintain their own email server environment.
The best part is the support around setup and infrastructure management. Users often mention the time saved compared with setting up domains, SPF, DKIM, DMARC, mailboxes, and warmup themselves. Some reviews also report deliverability issues, so performance can vary by setup.
Mailscale starts at $79 per month for up to 15 email accounts. Higher plans increase account capacity, while enterprise requirements can use larger custom setups.
Mailscale has 90+ reviews on Trustpilot with a 4.3/5 rating at the time of writing. Users often mention hands-off setup, time savings, responsive guidance, and lower operational work compared with building email infrastructure themselves.
Read Mailscale reviews on Trustpilot
Mailscale is useful for agencies and outbound teams that want managed infrastructure without running their own email servers.
It can also work well when reducing technical setup and maintenance matters more than having direct control over the underlying infrastructure.
In conclusion, I'd like to say that the right choice depends on how many accounts you need, what type of infrastructure you want, and how much control you need over your domains, IPs, and mailboxes.
Before choosing a provider, look beyond the monthly mailbox price. Check the infrastructure model, domain costs, IP setup, mailbox limits, warmup options, integrations, and renewal terms.
The best choice depends on how your outbound operation works today and how much infrastructure you expect to manage as it grows.
If you want a simple takeaway from this guide, I'd say try Mailforge if you want to build and manage cold email infrastructure without handling every part of the setup yourself.
Cold email infrastructure is the sending layer behind your cold email campaigns, covering domains, mailboxes, IPs, and authentication records. It is separate from the sequencer that runs your email and multi-channel outreach. Most providers on this list automate domain setup, inbox creation, and SPF, DKIM, and DMARC configuration. What differs between them is the IP model and what you pay as you scale.
Maildoso is the cheapest at higher volumes, at $225 per month for 300 mailboxes. Mailforge has the lowest entry cost at $3 per mailbox slot per month, with a 10 slot minimum. Flat-rate plans such as Inframail at $147 per month work out cheaper once your inbox count is high. Cheapest is not always right, since shared infrastructure carries reputation risk you do not control.
Shared infrastructure works while you are testing or running moderate volume, and dedicated IPs make sense once outbound is a core channel. On a shared pool, your sender reputation depends partly on how other senders behave, which affects where your emails land. Dedicated IPs give you full control over that, at a higher monthly cost. Infraforge and Inframail are the dedicated options on this list.
Plan on around 2 to 3 mailboxes per domain, then work backwards from your daily sending volume. At a safe ceiling of 15 to 20 emails per mailbox per day, 30 mailboxes covers roughly 450 to 600 sends a day. You scale by adding mailboxes rather than pushing more volume through the ones you already have, which is what trips spam filters.
With several providers yes, but not with all of them. Mailforge, Primeforge, and Infraforge support free domain transfers. Maildoso and Inframail let you connect external domains or buy new ones in the platform. Check this before you commit, because moving away later is harder when the provider holds your domains.
